Trade in values are by what they refer to as "Black Book", meaning they will give you what they would buy from another lot for or auction price. Like stated before, if it's a high demand car, you'll get more. Obviously they're not gonna give you private party value. They have to make money on it too. And unless they are getting your car as a trade in you're likely not to get as much either. But that's all lots.
Also when a car hits the lot it's had any major service needed performed. If it needs paint, they paint it, all cars get brake jobs, tires, and actual detailing, oil changes, etc. Do you pay more? Yes. Is it worth it? IMO yes. It's not a hole in the wall lot that just hoses a car off hit it with some Armor All and calls it good. I was a skeptic for a long time, then my company got them as a customer for services that we provide. Got the tour, and how/what they do for take in processes. Good stuff.