If you are asking whether your LEGO business is actually growing, the honest answer is that revenue alone will not tell you. A month with higher sales can still be a step backward if your fees went up, your time invested doubled, or half that revenue is sitting in unsold inventory. Real growth in LEGO reselling shows up in sell-through rate, profit per hour, repeat buyers, and inventory turnover, not just the number at the top of your sales report.
I've been selling LEGO across eBay, Whatnot, BrickLink, Facebook Marketplace, and Instagram for years, and in my experience the sellers who scale past a hobby income are the ones tracking the boring metrics, not just the exciting sales screenshots. This post walks through the numbers I actually look at, why revenue can lie to you, and a simple monthly checklist you can start using today.
- Revenue growth without profit growth usually means rising fees or falling margins
- Sell-through rate matters more than total items listed
- Follower growth on Whatnot and Instagram only counts if it converts to repeat buyers
- Inventory turnover tells you how much cash is trapped on your shelves
- Marketplace fees can quietly erase what looks like growth on paper
What Actually Counts as Growth in a LEGO Reselling Business?
Real growth means your profit per hour worked is going up, not just your total sales. A business that made $5,000 last month and $6,000 this month has not necessarily grown if it took twice as many hours, twice as many marketplace fees, or left more unsold inventory sitting in bins. Growth has to be measured against time, cost, and cash flow together.
I learned this the hard way early on. I started tracking hours spent sorting, photographing, and packing, and I noticed that some of my highest revenue months were actually my worst months in terms of profit per hour. A slower month with better sell-through and fewer returns often beat a busy month with a pile of dead inventory left over.
Is Revenue Growth Just Hiding Rising Costs?
Rising revenue can hide rising costs, especially marketplace fees, shipping supplies, and promoted listing spend. If your top line revenue is up 20 percent but your fees, packaging, and ad spend are up 30 percent, your business is shrinking in real terms even though the sales chart looks great. You have to look at net profit, not gross sales.
This matters a lot on eBay specifically. eBay can put your listings in front of millions of buyers, which is part of why it has been the backbone of my own reselling since the start, but promoted listings can push your total take rate close to 25 percent of a sale once you add standard fees on top of ad fees. A seller I know doubled his eBay revenue in a year but barely moved his profit because he leaned heavily on promoted placements to get there.
Heads up: This is not financial or legal advice. We're sharing what we've learned from the LEGO reselling community.
How Do You Measure Sell Through Rate, and Why Does It Matter More Than Sales Volume?
Sell through rate is the percentage of listed inventory that actually sells within a given period, and it is usually a better growth signal than raw sales volume. A seller who lists 100 items and sells 80 is in a healthier position than one who lists 500 and sells 120, even if the second seller's total revenue number looks bigger on the surface.
To calculate it, divide items sold by items listed over the same window, then track that percentage month over month. If your sell through rate is climbing while your average sale price holds steady or improves, that is real growth. If you have to keep adding more inventory just to hit the same revenue, your pricing or sourcing needs work. Checking recent sold data on BrickLink and BrickEconomy for your categories before you price is one of the simplest ways to keep sell through healthy, since both track actual completed sales rather than asking prices.
What Does Inventory Turnover Tell You That Revenue Doesn't?
Inventory turnover tells you how much of your cash is actually working versus sitting on a shelf, which revenue alone cannot show you. Two sellers can have identical monthly revenue while one has $2,000 tied up in slow moving stock and the other has $20,000 tied up. The second seller is not really growing, they are just accumulating inventory risk.
In my experience, this becomes obvious the moment you actually total up what you are holding. I recommend running your full collection through a proper valuation at least once a quarter rather than guessing. Tools like brick'em's LEGO collection value calculator make it fast to see your total inventory value against what you have actually sold, so you can spot when growth in sales is outpaced by growth in unsold stock.
Should You Track Follower Growth on Whatnot and Instagram?
Follower growth is worth tracking, but only as a leading indicator, not a growth metric on its own. Followers only matter if a rising share of them turn into repeat buyers and higher average order value over time. A bigger audience with the same buying behavior is not business growth, it is just a bigger number.
My own numbers back this up. My first Whatnot show had about 10 people watching and did over $500 in sales, which felt like a big win at the time. From there I reached 3,000 plus followers and more than $30,000 in sales in five months, and the growth curve was not about follower count alone, it was about repeat buyers showing up show after show. On Instagram, trust moves even faster once it exists. I once posted a single story to around 700 followers and sold $700 worth of LEGO to three different buyers in about 20 minutes, because those people already trusted me from past sales.
The lesson: track followers, but track repeat buyer rate and average order value right alongside it. If followers go up and those two numbers stay flat, you have an audience problem, not a growth story.
Are Marketplace Fees Quietly Killing Your Growth?
Yes, fees can quietly kill growth if you never compare take rates across platforms, and this is one of the most overlooked LEGO business growth metrics. A sale that looks like a win on one marketplace can be a loser once you account for final value fees, payment processing, promoted listing costs, and shipping subsidies.
From what I've seen, BrickLink tends to have much cheaper selling fees than eBay, which is part of why it works as the Wall Street of LEGO pricing data and a solid channel for lower dollar items that would not be worth shipping profitably elsewhere. Whatnot, on the other hand, has run no seller fee days at various points, and because it is still growing fast and courting sellers ahead of a potential future IPO, in my view the current fee environment there is unusually seller friendly and worth taking advantage of while it lasts. Facebook Marketplace charges no platform fee at all for local sales, which is part of why I still use it heavily for sourcing bulk lots. None of this should be taken as a guarantee those terms stay the same, so check current fee schedules on each platform before you build a strategy around them.
What's a Realistic Monthly Growth Checklist for LEGO Resellers?
A realistic monthly checklist covers profit per hour, sell through rate, inventory value, repeat buyer rate, and fee percentage, reviewed together instead of one at a time. Looking at these five numbers side by side each month gives you a much clearer growth picture than watching your bank balance alone.
| Metric | What it tells you | Where to check it |
|---|---|---|
| Profit per hour | Whether growth is worth your time | Your own time log plus net sales |
| Sell through rate | Whether inventory is priced and sourced well | Items sold divided by items listed |
| Total inventory value | How much cash is sitting unsold | brick'em collection value calculator |
| Repeat buyer rate | Whether your audience actually trusts you | Order history by buyer on each platform |
| Fee percentage of revenue | Whether platform costs are creeping up | Monthly fee statements per marketplace |
If you are just getting your inventory organized enough to track any of this, starting with a proper haul calculator on new lots before you list them will save you from guessing at margins after the fact.
What Mistakes Do Sellers Make When Tracking Growth?
The most common mistake is treating gross revenue as the only scoreboard, which hides fee creep, unsold inventory, and unpaid hours. A close second is ignoring minifigures and parts entirely because they feel small, when in my experience they are some of the most liquid, storage friendly inventory a reseller can hold.
I've noticed sellers also skip proper identification and end up under pricing rare pieces they do not recognize. Running new lots through the LEGO minifigure database before pricing them individually catches value you would otherwise miss, since a rare figure can be worth two or three thousand dollars while looking almost identical to one worth a couple of dollars. On the flip side, sellers who want to think longer term about which categories to hold rather than flip quickly often use an investment calculator to compare expected appreciation against simply reselling now, which is a different growth question but worth asking as your inventory value grows.
If you want a simple starting point, brick'em has a free sign up flow that gets your first lot scanned and valued in minutes, and the brick'em blog has more breakdowns like this one if you want to keep digging into the numbers side of reselling.
Frequently Asked Questions
What is a good sell through rate for a LEGO reseller?
There is no single universal number, but in my experience anything consistently above 60 to 70 percent over a rolling 30 to 60 day window suggests healthy pricing and sourcing. Lower than that usually means items are overpriced, poorly identified, or listed on the wrong platform for that category.
Should I measure growth monthly or weekly?
Monthly is usually more useful for LEGO reselling because sales can be lumpy around live shows, holidays, and restocks. I recommend a lightweight weekly check on inventory and cash flow, paired with a full monthly review of profit per hour, sell through rate, and fees.
Is follower growth on Whatnot a reliable growth metric?
On its own, no. Follower growth only reflects real business growth when it comes with rising repeat buyer rate and stable or improving average order value. Track all three together rather than celebrating follower count in isolation.
How do fees affect whether my business is actually growing?
Fees can turn a revenue increase into a profit decrease if they rise faster than sales. This is not financial advice, but from what sellers in the community report, comparing take rates across eBay, BrickLink, Whatnot, and Facebook Marketplace regularly is one of the simplest ways to protect real growth.
What is the fastest way to see if my inventory value is growing?
Run a full valuation of what you currently hold on a consistent schedule, such as monthly or quarterly, using a tool built on current marketplace pricing data. Comparing that total over time, alongside what you have sold, shows whether your business is actually building value or just cycling the same cash.
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