Bad analogy for wall mart to be compared to Tiffany.
One started out selling to the rich, and has basically stayed that way.
The other started out selling to the masses and has stayed that way.
Rich people for the most part do not shop where the masses shop.
Say what you will about wal mart, they do carry a lot of items at a lower cost to the consumer than other stores.
But back to banners and links on blogs/sites.
Bottom line, it is your visitors that determine whether you show high end stuff or low end stuff.
If your high end banner is not selling anything, but other banners and links to low end stuff (or less costly stuff, either way), then drop the high end banner.
And find lower cost stuff to take it's place.