> It's more cost-effective for Amazon to send a $50 shirt to the dumpster rather than resell it.
It's not a $50 shirt. It's like a $5 shirt to them, which some sucker is willing to pay $50 for. Used, it becomes a $10 shirt.
A dumpster can be found right in the neck of the woods of where the returning customer lives, whereas it may have to travel far and pass through more processing if it goes to another customer elsewhere.
It needs to be inspected, repacked.
There is a risk in every returned item. Sometimes people return a perfectly good item. But sometimes it's because there is something wrong with the item, such that the next buyer is also likely to return it, even if they get it cheaper.
Basically returned items are entirely outside of the profit-optimized delivery path. They incur costs and risks, at a reduced revenue.
I'd never return an item which matches the description and isn't damaged.
If it isn't damaged in any way but does not match the description, that's a problem; if it is sold with the same description, the next customer will also see that it doesn't match. A new listing has to be created for that product. Not gonna happen, or not in the processing time frame of that particular return.