I agree with Wink that most vendors participating- or advertising- here will offer a PS discount.
Plus it probably makes all the sense in the world to ask- common decency dictates a vendor should treat everyone well- but it can't hurt to let them know a buyer is part of this community.
To me, that's one of the very highest purposes of this forum.
Vendors should know if they don't behave well, consumers have a great platform to discuss it.