I've been reading about "auction culture" recently and it seems particularly relevant to sharing.

Auction culture is one aspect of e-bay's impact on buying decisions. People are increasingly aware that some luxury items can be sold after a year or so for a high percentage of the original price. So when they want a new version, or if they decide they don't need the item after all, they know they can recover much of the original cost. This can make the item better value than something that actually costs much less. So buying a Louis Vuitton handbag can be more cost effective than is immediately apparent to many people (and all men). Or, as explained in Futureshop by Daniel Nissanoff , how a $750 stroller (£350 pushchair to us Brits) can be the cheapest child transport option