But that's what happens when you make your clothes to sizes that have no relation to the bodies that go in them. Especially for women. What the fuck is a 12?
When I go to a shop, I try on maybe ten pairs of shoes that are all my size before I find a pair that fit my feet and I can actually walk in.
There's no waste there, it's like one extra journey to your house when you buy something, no matter how many things you're sending back. The real waste is when the shop just throw it away because it's cheap shit not worth processing back into stock.
If it's such a hassle, maybe don't sell clothes online. Put it back in the high street where it belongs.