To make my answer brief, not a lot. Maybe you'll get 5 dollars at best per game from GameStop.
its probably worth 189 dollars
R850
really cheap like 10 - 20
your best bet is to go to your local gamestop and ask for how much the games and the charger are worth.
Go to Gamestop.com and check their used psp sexction.
It depends on the game and how long since the game has come out.
The PSP Go will be all digital download, no cartridges. If you are someone who likes to buys used games or trade them in for other games, go with the 3000. Other than that, there doesn't seem to be too much of a difference.
The same as the cost would in a store for a PSP game.http://www.destructoid.com/psp-download-games-will-cost-the-same-as-retail-games-147396.phtml
Yes, you can play PSP games without a memory stick. However, if you're playing games from PSP UMD's (little PSP games in cases). If you want to play games saved in your PSP's hard drive, then no. So, pretty much by UMD, you can play games without a memory stick in your PSP, but you'll be unable to save.
When you buy a PSP game, it will cost you around 15$-30$ US.
No, the PSVita is a much more advanced console. Games made for PSVita are not compatible with a PSP.
300,000,000,000 $
Some of the cheapest PSP games are early sports games. Sports games come out every year. Brand new to match the year, so naturally the older games are not worth that much; therefore, they will be the cheapest PSP games to purchase.