It is literally the Walmart of warehouse stores.

Sam Walton is the originator of both Sam's Club and Wal(ton)mart.

Sam's competes more with stores like BJ's and Brandsmart than Costco, which is really in a league of its own.

Yeah, maybe it varies, but the local Sam's has gone way downhill over the last couple decades (I don't think income-demographics have changed much in the area over the same time-span, which makes that really odd) along with the three nearest Wal-Marts. Sam's is now firmly in the same relation to CostCo as Wal-Mart is to Target: basically the same thing, except everything about it is anywhere from a little to a lot worse (except, sometimes, the prices)

The parking lot at the costco near me is insane. Everytime I went there, I felt like I was going to get hit. Sure enough, an oldy was killed in the parking log shortly after I stopped going.