Come on!
They can make all the money they want by marking up the base prices.
And I am not convinced they don't mark up the base prices, despite what the rep at 1-877-HOTWIRE told me.
Burying phantom service charges in taxes to make money is fraud.
It is bait and switch. If a car is $21 per day, it should be equivalent to paying a rental car company $21 per day.