I managed a furniture and appliance store, we sold a lot of mattresses, and we hauled off the old ones, took them straight to the dump, under no circumstances would we bring a used mattress into the store or warehouse, bed bugs.
Plus, its illegal to sell used mattresses, so they have no value. Its also illegal for Good Will or the thrift stores to sell used mattresses that are donated to them, I don't know how much scrutiny they get, but we had inspectors in the store a couple times a year, looking for used mattresses and checking for state tax stamps, if our mattresses didn't have state tax stamps there could be hell to pay. One time we had a bunch that didn't have the state tax stamp, an oversight by the manufacturer, we got a written warning and advised they would be back in about a week to make sure the stamps had been affixed, and they were back the next week doing that, and we were in compliance when they rechecked.