Hmm, I know that when I once rented at West Palm Beach without coming in from the airport, I selected "I'm not arriving by Air/Train" in the reservation and some of the airport fees were not included in the quote. I'm not sure if it was a concession recovery fee or some other fee related to the terminal shuttle bus though. This was back when they used to take your name on the shuttle bus, so I presumed you couldn't use this as a "loophole" as they'd figure out if you did come in from the airport, and adjust the reservation as appropriate.
I don't think they get names on the buses anymore, though maybe they do in PBI.