Agreed, this guy is a thrift shopper and I feel what he is doing is legit, he's competing at a lower level where the books are sorted to value.
Having worked in a high-end, selective used bookshop, there is a lot of arbitrage and upselling and in many cases it is worth it. It costs money to cull the good stock and resell it. You're also correct about market: one of my fave bookshops is a converted barn and the front foyer is often full of books from broken up libraries which were brought direct from an estate and not sold at the auction.
Having worked in a high-end, selective used bookshop, there is a lot of arbitrage and upselling and in many cases it is worth it. It costs money to cull the good stock and resell it. You're also correct about market: one of my fave bookshops is a converted barn and the front foyer is often full of books from broken up libraries which were brought direct from an estate and not sold at the auction.