If you click on the "Travel Reservations" on the top of this page, you can quickly see the range of prices offered by the various rental companies.

Personally, I don't recommend paying for the navigation option in rental cars -- being able to read a map is a good skill to develop and has the huge advantage of enabling the user to discover attractions and places that electronic doo-dads can not yet match in North America. Here are our recommendations for atlases in North America.

Mark