Each platform handles shipping differently. Here's what actually saves money on each one.
Use calculated shipping so buyers pay exact cost based on their ZIP. Set handling time to 1–3 days. eBay's shipping discount is built in — you'll pay commercial rates automatically. For items under 1 lb, USPS Ground Advantage wins almost every time.
Poshmark provides a prepaid USPS Priority Mail label for every sale — buyer pays the flat $7.97 shipping. You don't choose the carrier. This works great for lightweight clothing; for heavy items it can eat into buyer interest.
Mercari uses weight-based flat rates via USPS or FedEx. You pick the weight tier when listing — if you underestimate and the label doesn't cover actual weight, Mercari charges the difference. Weigh everything before listing.
For shipped items, Facebook uses prepaid USPS or FedEx labels — buyer pays actual shipping at checkout. Local pickup has no shipping cost at all. For large/heavy items, local pickup is almost always the right call.
OfferUp ships via USPS with flat-rate tiers: $4.99 (0–1 lb), $7.99 (1–5 lb), $13.99 (5–20 lb). These rates are competitive but non-negotiable — you can't use your own Pirate Ship account.
Set up calculated shipping profiles by package size. Etsy discounts USPS and FedEx rates. For handmade/vintage items, USPS Ground Advantage is usually the cheapest. Avoid flat-rate boxes unless your item fills them completely.
Use Pirate Ship for any platform that lets you upload your own label (eBay, Etsy, Depop, Grailed). Pirate Ship offers Cubic Pricing for USPS Priority Mail — on small, heavy packages it's 40–60% cheaper than retail. Free to use, no subscription.
Both platforms let you set your own shipping price and upload any label. This is where Pirate Ship shines — buy a discounted label, set your shipping price to cover it (or slightly under to attract buyers), and pocket the difference.