When I first started selling my handmade ceramics on Etsy, I thought the hardest part would be the actual crafting. I was wrong. The real headache was the math. I remember staring at my dashboard after a busy holiday weekend, seeing a bunch of sales, but having absolutely no idea what my actual take-home pay was. I was manually typing numbers into a messy spreadsheet, trying to account for listing fees, transaction fees, payment processing, and the dreaded offsite ads. One misplaced decimal, and my profit projections were completely off. I was spending more time doing fee math than making products. So I decided to build something.

The Hidden Cost of Marketplace Math

The problem with marketplace fees is that they are rarely a single flat rate. On Etsy, the fee structure is a labyrinth.…