Jonah Lehrer, the author of Proust Was A Neuroscientist (which I have) and the new book How We Decide (on my wishlist) has an interesting article on the Frontal Cortex science blog regarding Costco and how it affects our decision-making regarding pricing.
To which I contributed this in the comments:
You should study my wife – she is immune to the Costo effect & calculates everything, even there. I swear she has a terminator-like data screen across her vision that just adds up whether something is a good deal or not and rejects stuff out of hand, because she’s so quick and so good at the money.
It make shopping trips painful, though. I bring stuff with my lizard brain to the cart and say “I can has?” and she scans it and says “no, honey, this isn’t a good deal. Put it back.” and I schlep off to put it back and come back with some other shiny thing I found to repeat the process. Six hours later, she finally gets to check out with the 3 things she actually came in for.