I'm going to admit, I do have a $1500 Prada bag.
For me, it was worth every penny. I wear it pretty much every day, and it dresses up and down. The material is such that I can take it to the park with me and put it on the grass without worrying about ruining it. In fact, that was what planted the seed in my head originally: I ruined a really nice leather purse by putting it on a tree stump and getting sap all over it.
It also just makes me feel great every time I wear it. Even if I look awful and I'm wearing sweatpants, I pick up the bag, and I'm like, "don't even think of messing with me or my awesome Prada bag."
The only thing I didn't consider was that I can't drop it off at the shelter when I walk dogs, because the purse is far more valuable than the contents. So I'm looking for a cheaper casual bag for that. Also, I have a purse obsession.