A quick note on the numbers: they're just examples in a stand-in currency. Use your own, the math works exactly the same.
Most makers decide what to make the same way they decided what to make last time: by what they enjoy making. That's a lovely way to spend a craft and a quietly expensive way to run a business. The thing is, you're already sitting on the answer. Every market you've worked has been telling you what people actually buy. You just have to read three numbers to hear it.
The three numbers that matter
For each product, you want to know how many you sell, how much profit each one earns, and how fast it moves. Units sold tells you what's popular. Profit per unit, which is price minus your real cost, tells you what's worth your time. Sell-through, how quickly your stock empties, tells you whether you're making too few or too many. Popular, profitable, and fast are three different questions, and the products that feel like winners often only win one of them.
Your bestseller might be your worst earner
Here's the trap that catches everyone. The little $4 impulse item flies off the table, so it feels like your star, while the $30 piece sells slowly and feels like a dud. But earnings are units times profit, not units alone. Sell forty of the $4 thing at a dollar of profit each and you made forty dollars. Sell eight of the $30 piece at twelve dollars of profit and you made ninety-six. The slow one quietly out-earned the popular one by more than double. Without the numbers, you'd have made more of the wrong thing.
Find your heroes and your dead weight
Run the numbers across a season and a pattern almost always appears: a handful of products earn the bulk of your money, and a long tail barely moves. Those few heroes deserve your time, your best table space, and some close cousins, new colors, sizes, or scents of the thing that already works. Meanwhile, anything that hasn't sold in several markets is dead weight. It's tying up cash and materials and crowding the very items that do sell. Mark it down, clear it out, and stop making it.
Keep an eye on the calendar, too
Some products aren't slow, they're seasonal. The thing that flops in July sells out in December. Tracking when things sell, not just whether they sell, keeps you from retiring a winter hero in the summer. Give it a full year before you call something dead.
One exception worth keeping
Not every product has to earn its keep in dollars. A striking signature piece can be a slow seller and still pull people to your booth, where they buy the heroes instead. That's a real job, and it's worth keeping one or two around as the work that makes people stop. Just know that's the role it's playing, so you keep it on purpose rather than by accident.
Make what you love by all means. Just let the numbers, not the guesswork, decide how much of it to make.
None of this works from memory, because nobody can hold a season of sales in their head. It works from a record. Wares logs every sale and knows the cost behind each product, so it can show you the movers, the earners, and the dead stock without a spreadsheet, and you walk into your next making session knowing exactly what to start. It's free to try, right in your browser.