I had bought a brand new Denon receiver from a b&m store quite a few years ago and a few months later costco had same receiver selling at nearly half of what I had paid for mine, I was pissed.
I actually put in a call to Denon in Canada , and was told that Denon receivers sold at costco were considered Grey Market by Denon Canada , and they would not honor the warranty.

I don't know if it is any different now .

Al