Most used gear dealers need to mark up around 100% (inc taxes) to make a living. If you think about it, if they pay $75 and sell the used iPad2 for $150, they make $75, they pay, say 7% tax ($10) need to offer a warrantee (say a 10% in warrantee fail rate = $15), pay staff and rent and insurance and all the other costs of running a business (possibly another $15-30), a total of maybe $55 on something they may have cluttering the shelves up for several months (and which may suddenly become worth half what it was when they bought it if somebody releases another new, better product) which may realise $20 profit at the end of it all (but also may only sell for $100).
OTOH ebay charge 10% on completed sales and an extra 8% if you accept payment by paypal, that means they take 18% of sale value... plus postage (which you have to pay). Assuming you sell the iPad for $140 and charge your cost of $10 postage, you'll receive $123, less your $10 postage costs so $113. It's still a huge chunk of what you sold the iPad for but a little better than the dealer. Of course if he pays you $100 it's probably not worth the gamble on good old feebay 'cos it may only sell for $120.....
