Any more specifics on the hardware? I know that by now certain 3000-series PSPs can load CFW, and if yours is one of the models that can run CFW, I'd certainly consider it more worth the price than one that only runs OFW.
That being said, Sony just slashed PSP prices by about 40 bux across the board, so you can get a NEW PSP for about 130 USD. At this point, you're only selling to collectors. You might then want to try to stick close to the rest of the market - undercut it by a little, but if it's too much of a bargain you might scare them away on suspicions of counterfeit hardware or the likes