Also, there are "buying mistakes" and gifts to consider. I have at least four handsome handbags in my closet that have never been touched (not to mention about a dozen pairs of Ferragamo shoes!) They aren't Hermes, but I'm sure some people with a lot more disposable income than me make mistakes or get presents from their parents and decide to sell them.
One other thing to consider: jemznjewels is in NYC, where fashion industry insiders are given bags they haven't asked for and where bags used briefly for photographic shoots or commercials are quickly retired.