How much do car dealerships mark up prices?

It varies significantly with the popularity of the vehicle. If a model is flying off lots, the dealers won't come down very far from the sticker price. Try checking "True Market Value" on web site Edmunds.com to get a ballpark idea what you should expect to pay for a specific vehicle.

It also depends on the dealer. Some places (like carmax, for example) won't negotiate at all. The sticker price is the price you'll pay (plus taxes, fees, etc). Most dealers, however, EXPECT you to negotiate. I know that some people feel uncomforable haggling and if that's you, then go to one of those no-bargain places. Otherwise, go in expecting to play "let's make a deal."

Cars.com also have a feature to suggest a price you should pay for a new car. I used it when I bought a car a few years ago.

try reading this article: http://www.edmunds.com/advice/buying/articles/42962/article.html

it talks a lot about what salespeople do, how (much) they mark up prices, and the edmunds.com website also lets you search for information on whatever car you're looking for