Along the same lines, a researcher found that prices were actually cheaper at Whole Foods than at nearby industrial-scale supermarkets.

The impression of expense at Whole Foods comes more from the lack of low-priced products in a category and the multiplicity of high priced products in a category.
For head-to-head of the exact same item, Whole Foods generally came out cheaper.
They cited the example of frozen orange juice concentrate, which was the high end alternative at the monster supermarket but the low end option at Whole Foods, who would also squeeze you stuff to order.

The study was done a while ago, so the result may be a little different.
Either way, it's a nice reminder of the importance of range selection.

I always liked the story of strategic restaurant menu design.
Lots of dishes at (say) around $25. Steak at $40, and lobster at $60.
The lobster isn't there to be sold, it's there to make the steak look cheap--the goal being to sell lots of $40 steaks instead of the humdrum $25 dishes.

Jim