It's too bad that the NTTA only issues sticker TollTags and not physical transponders.  At least the E-ZPasses used on the East Coast can be taken from car to car with the proper case, enabling you to use toll roads without paying the rental car company's markup.  Better yet, Orlando's E-Pass has a Visitor Toll Pass designed to help tourists in rental cars avoid the rental car company markup.  Here, rental car users either have to avoid the toll roads or get ripped off by rental car company fees, as it is impossible to take the sticker TollTags from one rental car to another.  Granted, it's also a lot harder to avoid tolls on the East Coast (good luck visiting New York City or New Jersey without paying a toll!), but at least you can avoid paying the rental car company markup there if you plan ahead.  If only NTTA would do something like that here.