Seems like a reasonable price for some classic games.
Steam says they are "100% Windows 2000/XP/Vista-compatible", which can be one of the issues if you get an original copy of some of the older games (or don't want to mess around with 3rd party add-ons).
QUAKE III Arena
QUAKE III: Team Arena
QUAKE II Mission Pack: The Reckoning
QUAKE II Mission Pack: Ground Zero
QUAKE Mission Pack 2: Dissolution of Eternity
QUAKE Mission Pack 1: Scourge of Armagon
DOOM 3 Resurrection of Evil
Master Levels for Doom II
Return to Castle Wolfenstein
HeXen: Deathkings of the Dark Citadel
Heretic: Shadow of the Serpent Riders
Spear of Destiny