I worked for Nordstrom for a few years and one stat about returns that I heard was absolutely wild. Apparently something like 80% of all dresses sold got returned.
A lot of this was because people would buy an expensive dress for a single event and only want to wear it once, but people would also order a few sizes and just return the ones that didn't fit.
We worked on a few different things to make the latter process a little better for the consumer and cheaper for the business. A fun solution was allowing you to set up a reservation for a dressing room at a local store. You would choose a bunch of items and then "reserve" them to try on. Once you made the reservation someone in the store would go pick the items in various sizes and get them ready for you. When you arrived at the store, a dressing room with your name was ready and (if I remember correctly) you could just walk out with the items you wanted and leave the rest.
I'm not sure this experience ever made it outside of a few stores in the Seattle area.