Interesting, I've definitely been motivated by the 'one pair left' message on Amazon with regard to a pair of shoes at a discounted price in the past. I think in some ways that consumers (or at least I do) take home more things from thrift and off-price retail or sale outlets because there is no consistent stocking, it's luck of the draw what is there one day over the next, and I feel comfortable with the return policy but afraid of 'missing out' on a good thing at a great price.
I haven't been as motivated by the same thing at retail price however, partly because I feel that there really are numerous choices that will satisfy the same need, and that 90% of the time I can find what I want without paying the markup.