And unless... a bunch of other factors. They can say "it's cheaper than the store" if it's cheaper than one store somewhere in the middle of nowhere since they don't mention what store they're talking about.

It has nothing to do with WA. I bet if it has to cross the Rockies, and end up anywhere in the West, it's going to cost about the same and if they can ship it to you without ever getting on aircraft (that's the key) than it's going to be cheap shipping.