What you really should look for is something called invoice, the price dealers pay for a vehicle. Unfortunately, the invoice price isn't totally trustworthy either because cars can be bought lower than invoice price, but invoice is always lower than MSRP. Of course, like MSRP, invoice prices have ranges because of vehicle options, so websites with invoice prices that inclue options, like Autobytel, are a good place to start. There are MANY, MANY, MANY other websites you can use as well.
Recently, I wrote about the Hummer using a 2007 MPG rating for 2007 cars. A lot of comments thought I was being unfair and they were right. Your mileage will vary and the number on the sticker actually has a range; +- 3 MPG for city and +-4 MPG for highway. The point I am making is don't trust a thing in car ads; not price, not MPG, not a thing! You should always do research before you buy a car.