>You can find silly faults with individual examples all you want, but studies indicate that people have a tendency to think percentage-based about savings rather than absolute terms.

Which sounds like the smart way to go about it.

It seems a little illogical in the chocolate vs laptop $.50 off voucher, but it too makes sense. The laptop voucher provides almost no value to you, considering you are about to spent $700 dollars on the thing anyway. $.50 could be just the gas to go to the store to buy it.

$.50 for the chocolate on the other hand, will be taken only by cash strapped people (or coupon maniacs).

I doubt people with $700 at the ready to buy a laptop would at the same time clip a $.50 coupon for a chocolate bar.