I don't know if I agree that there is no such thing as a bad prime rib, but there are definitely some better than others and many not worth what they might cost. I've never bought any meat from Sam's. I've seen some at Walmart I wouldn't buy.
But to be fair, errthanges so expensive now I don't even know what to tell you is a good price on a select prime rib.
I think if it looks fresh and looks good and is at a price you think is good or even a deal, jump on it.