Hotwire and Priceline use major Brand name Car rental agencies,
Between them I have received Budget Hertz Alamo Enterprise and Avis.
Priceline and Hotwire charge their own Service Fee for themselves.
They act as the middleman in the transaction, hence the fee.
The fee is a minimal compared to the savings you CAN get using either
one of those companies.
Priceline has a different formula to set fees for your requests than
Hotwire does.
They are similar but not always the same price.
The one good thing is that the FEE is charged just once per booking.
For a car rental or hotel stay, it the same fee for no matter how many
days you rent or stay.
The bad thing is that if you rent just one day, you pay the same fee
as the next guy who rented for 2 weeks.
It averages out to usually be 5-7 dollars.
Within those numbers, SOMETIMES its less expensive to rent
traditionally.