I have a couple friends who buy pallets and pallets of returns from most of the big online retailers and big box stores. Then the just sell almost everything for $5 each in their shops. Occasionally I have seen them post that they needed a new fridge so they bought a couple trucks of returned fridges, picked one for themselves, and then sold the rest super cheap.
The $5 method seems pretty foolproof. If you know you are getting 100 items on the pallet and you know that 80 or 90% are going to be resellable for $5 you know just what you need to bid to remain profitable. Don't need to worry about trying to squeeze a bit more profit going through every product and figuring out if something can be $10 or $20 or whatever.
I know returns are huge at my day job. When I first started 10 years ago the returns would come in, someone would look through them and if the tags were still on and they hadn't been worn they were put back in inventory. Not really sure what happens with returns now. I know last year we did some big events at some stadiums around the country where we gave away over 300,000 items to low income families and charities. Even had a popular hip hop artist Lil' Baby write a song about it. I really liked that approach. Just because a shirt didn't fit me or someone pulled the tag off a hoodie before they realized it didn't fit doesn't mean someone somewhere couldn't use it. So we turned those 300,000 items (not sure what % that is of all our returns) into a ton of publicity, kept the stuff out of landfills, and helped people who couldn't normally afford new gear for their team.