The cost of a rental car depends on many different factors: the class, the availability, whether or not you're looking for extra's such as GPS or additional insurances, and so on.
Of course, when you're booking your car, you can see exactly how much it will cost, including where the costs come from. That's why you'll never have to deal with unexpected charges when booking via Enterprise.
For more information on surprise costs, please feel free to check out the video below or the concerning help article: Are there additional charges that are not mentioned online?