Wow. Those are pretty good prices. Looking at the Bridgestone Turanza Serenity in 195/65R15, Roadway is $94.90 each plus $36 for shipping, or $415.60 delivered. Plus, say, $50 for installation, and I'm at $465.60 installed. Not bad!
Tire Rack is not even close, at $110 each, and $44 for shipping, for a total of $484. Or $534 installed. Loser. I've never found Tire Rack to have the best price on a set of tires...EVER. This is no exception.
Even Firestone Complete Auto Care beats Tire Rack, at $109.99 each. Even if they charged $20 EACH to install (they don't), they're still at $520 out the door.