Shopping for me is not about accumulating more or nicer things. It's about the hunt. I take the following things into consideration: how much is it worth, how much will I pay, how hard did I have to look, how rare is the find. This isn't to say I don't like a good ol' GAP attack - easy, fruitful and common - but my favorite pieces, the ones I cherish most were expensive to someone, cheap for me, in the corner or crazy basement and have never/will never see again.
Or in the case of the Balenciaga below, it's worth a bundle, I paid $20 at a women's shelter, then twice that to have it repaired, plus I have been eyeing the real deal for a lifetime. Chalk that up to a major score!