Warning! Bling!
A recent study in the Journal of Consumer Research (which is summarized here and here) purports to explain why women buy luxury handbags.
The authors posit that such luxury goods are way for women to signal to other women that their partner is devoted to them. As one of the authors explains, “"A designer handbag or a pair of expensive shoes seems to work like a shield, where wielding a Fendi handbag successfully fends off romantic rivals."
This, of course, assumes that a romantic partner made (or contributed to) the purchase. When study participants were told that the woman bought the handbag with her own money, the “warning power” of the item vanished.