Who goes to garage sales with the intent of paying market value for anything? Ebay targets specific markets and the bidding among buyers within that specific market determines the auction value for merchandise that was often bought at bargain prices at garage sales. Garage sales are a crap shoot for bargain hunters, they are a matter of convenience for both the buyer and the seller. If you want eBay prices for something, then take the time to sell it on eBay to someone who is looking for that particular item. If you are more interested in making fast money via the garage sale route, then you should price your stuff in a range which makes it attractive enough for quick purchase by impulse buyers or bargain hunters.
Yes! Unfortunately, this fails to account for the vast majority of people that are illogical, obtuse, or both.