If you have a couple Half Price Books close by, sometimes they have PSP systems in the cases by the registers. There's 50% off coupons if you're on their mailing list for this Sunday that'll apply that (I think) would put it right around $35-$40 for a PSP 3000. I was thinking about picking one up just to play around with that-which-shall-not-be-named here (although I don't think that there are mods anymore, so I'll just say cfw and call life good).
All that said, there was just a $128 probably new but dented box Vita on AWD for $128 and a Vita is a waaaay better piece of hardware if you're looking for a handheld. Better to spring for that if you've got the scratch.