Most "how to start an online shop" guides quote you the listing fee and stop there. That number is real, but it is not the number that determines whether your first three months are stressful or manageable.
The fees platforms actually mention
- Listing fees: small per-item charges that add up fast if you list a wide catalog on day one.
- Transaction fees: a percentage taken off every sale, before payment processing.
- Payment processing fees: a separate cut taken by the payment processor, on top of the transaction fee.
- Currency conversion fees: relevant the moment you sell internationally, easy to miss when budgeting.
The costs that don't show up in the fee schedule
Packaging that actually protects the product, a shipping scale so you are not guessing at postage, decent product photos (even a $30 lightbox beats a kitchen counter), and the software you will inevitably need for order tracking once you pass a dozen orders a week.
A realistic first-month budget
Plan for platform fees on your expected sales volume, one round of proper product photography, basic packaging supplies, and a simple system (a spreadsheet is fine at first) for tracking orders and costs. Most new sellers underestimate the packaging and photography line items the most.