Last year, I sold my PSP for an N800 too. Although I think I was very unlucky on eBay, as I only got a little over £100 for my PSP, 17 UMDs, and loads of accessories including the camera and a 4gb card. Bought an N800 brand new on play.com for £145...

But anyway, what I'm trying to say, is I think you're being pretty hopeful with the price. PSPs are old tech now, and I don't think you'll get much for it at all, especially with just the bare bones like you have.