Not sure if these are on Steam (and I don't care if they are or not), but these match your criteria, more or less:
Jagged Alliance 2 (1.13 overhaul is awesome) Silent Storm Fallout: Tactics Temple of Elemental Evil (Co8 overhaul, ftw) Fallout 1 and 2 (use Killap patch for the 2nd) Arcanum (use the mod that makes the fonts larger) Pool of Radiance: Ruins of Myth Drannor (patch it, use speed mod)
Wasteland 2, it's in early access now and it does cost $60 because they didn't want the Kickstarter backers to feel cheated by early access. They did say the finished version will be cheaper. It's a turn based strategic RPG. You create a squad of 4 characters with a lot of potential for builds. The combat is similar to Xcom. You want to know where you are at all times, like make sure you're in good cover for shoot outs and be ready for melee enemies as well. There's also a lot of persuasion options you can put points into such as bad ass, smart ass, kick ass, hard ass, and kiss ass, but make sure you say the right thing or some people can get pissed off.
I belong to the blank generation - Richard Hell http://www.last.fm/user/akuma634\