How much will i get trading in my fat original psp?

ive seen a weekly ad and called up gamestop about the $25 bonus theyll add with any hardware trade in. Should i try trade in? ive seen other questions concerning trading in the psp, and they said 30-60 bucks, and probably i can get 55-85 bucks, overall i bought this psp for 80 bucks, but what should i do? i tried selling it on craigslist, ebay, and no ones buying it.