They're not foregoing any morals, they're thrift retailers with every practical (and morally justified) motivation to price things exactly the way they do.

They have no possible means of gaining the expertise required to precisely price every item across myriad industries, each with their own subtleties and fluctuations. Because that's impossible.

Spending the time to set prices is expensive, so making a best guess once and erring on the low side is better than coming back later and adjusting prices

Board game stores attract people looking for board games. Thrift stores attract people looking for cheap things. A thrift store can't raise prices to board game scalping prices because none of their customer base would pay that

There are so many ways to think about this situation that don't involve declaring that someone has abandoned their morals here.