I cannot remember the name of the one we used, but we got a very good deal by getting it online in advance. We did not go for the drop off at the terminal, we did the drop off at their lot then take the bus to the terminal, when we got back, we phoned them, and they came and picked us up at the terminal on the bus and took us to our car. It was a few years ago, 2008, so I don't remember the price, but it was dirt cheap. Don't leave anything in the car, even map books can go missing, take everything of value out of the car before you leave home.
The going rate for parking seems to be 500/day if you drive around there and see billboards.
All the ones I looked at are basically the same. I've used a couple. USA was OK, but was a bit crowded to me waiting for the bus. Not as friendly as i would have hoped so have since gone to CoCo parking. Similar price, bracketed by duration, so pricing is pretty easy. Plans are based on pickup/drop off or not.