Work out what you really keep from a sale before you price it. No sign-up.
Final value, per-order and Promoted Listings fees by category, with or without an eBay Store, then your profit or the price to list at.
Commission, processing, payout and profit for a sale, or the price you need for the profit you want.
Material, power, printer wear, failed prints and your time, then the price to charge where you sell.