My honest opinion? I wouldn't touch it. Reasoning?
1) Not a fan of disc-only games, especially for PS2 which can still be found complete quite easily.
2) Heavily scratched discs = non-working discs.
3) Missing paint on the front of the discs = non-working discs.
4) 800 unique titles means probably 300+ versions of Madden, NBA2K and lots of other worthless sports titles.
5) Rental stickers on the top ruin the value of the games. Trying to remove them = yanking paint off the disc.
6) There are a lot of crap games on the PS2. I highly doubt you are looking at copies of Valkyrie Chronicles 2 or Dark Cloud 2 hidden in there.
It might sound harsh, but I wouldn't pay more than $200 for that lot and probably not even then. It would be more work than was worth the effort and you would have to polish every game to ensure they work. Disc-only PS2 games are practically worthless unless they are something pretty rare.
Stay away. Stay far, far away.