I may willingly pay more at some small Mom & Pop type stores that are struggling against the firmly entrenched oligarchy that undersells them. Such as a WalMart - which drives small, family-owned, shops into oblivion and ruining the charm of the small towns that have these monsters in their backyard.
Same goes for bike-shops. If you have a truly outstanding LBS, I'd pay the extra coin to keep them alive. Shops like these are gems and should be cherished in my opinion.