Rental cars at airports always cost more. Airport authorities add extra fees that are then passed on to rental car customers. Those fees don't exist at non-airport locations. The trade-off is a location further away from the airport and a longer shuttle ride.
We have used a number of rental car companies over the years, and more recently, we find ourselves using Enterprise. They often have the best (or very close to best) rates, and unlike other rental car companies, they will come pick you up if needed. Due to their popularity, however, they seem to have longer lines at the check-in counter more frequently.
What size of car did you sign up for with Enterprise, if I may ask?
CaT