I just brought my TC3 RTR kit back from the dead today. I'm running in the VTA class with it. Very capable platform for VTA and USGT classes.
A good clean Factory Team TC3 that is nearly mint can still pull $125 or so. Condition and FT versus RTR versions dictate the overall value, if you get a clean RTR chassis look at $100 shipped at most. If the TC3 has seen some high mileage you can probably get it for $70ish shipped.
Parts are still available through Towerhobbies, RCSPEED.net, and ebay. You can get most parts from those 3 sites, some aluminum upgrades are also still available as well.
If you aren't comfortable with the TC3, Associated still sells the TC4 as a Club Racer and parts are readily available just about anywhere.
Associated TC3 VTA & TC6 USGT