I sold cars for a short time and hated every minute of it.
In 1998 we were selling Jeep Grand Cherokees for $500 under factory invoice, Cherokees for factory invoice and Wranglers at $500 over invoice. This gave the dealer roughly $1000 per sale from factory to dealer incentives (kickbacks).
The Ford and Dodge Diesel P/U's are minimum $4000 markup on the monroni (factory window sticker)
I don't know what the specifics on the Tahoe/Yukon are as I didn't sell new GM's
NEVER pay a so called market value adjustment. pure BS just more profit.
Never let the lot get your financing, you can almost get 2 to 4 percent better on your own, unless you have bad credit. The factory special interest rates are ok.
There is a lot more room for the dealer to move in price on used than new. As a saleman I made $150 flat on a new car, unless it was loaded and we held the sticker w/no trade. Used, I made 30% of the net profit. Made over a grand on more than one.
Extended warranties are a big money maker for the dealer, if you want one then really deal hard on it.
The salesman is trying to make a living, he does that by selling you a car, most will try to turn you (put you on a different car than what you came in for) if they don't have what you want.
Don't let them change salesmen on you, stick with the first one or leave. The salesman cannot commit to anything unless the salesmanager tells him to. So you are really dealing with the sales manager the salesman is just the go between. the 4 way sheet is a way for them to spin the numbers on you to get as mauch as they can. We used to say that if someone said they could afford $250 a month that they could actually go $400.
Read the fine print, make sure it is a simple interest contract, and that it is not just the interest that is being paid off first.
If they try to take longer than 30 minutes to negotiate the deal after you have settled on the vehicle get out, they will try to wear you down and switch numbers on you. Make sure if they haven't secured financing for you when you leave that the "purchase agreement" has a clear return clause if the financing is not exactly what they promised. As a matter of fact, I would refuse delivery until it was solid.
Remember, you are in the drivers seat, and they need your money.
good luck
BTW trades, they start $1500 back of wholesale bluebook and take off for everything they can find, spots, dents, etc... They will use different ones for different things. Trades are a big topic all to themselves