In lieu of cab, I have been successful more than once (you can search my posts in this thread; I suspect it's been at least five times) of having Hertz foot the entire bill of a regular one-day/one-way rental, plus gas when I was stranded at the airport. In each case, that cost was over the $50 taxi cap. I think I make persuasive arguments that 1), it's nigh impossible to get a cab from an airport lot and 2), most of my rentals are late at night.

I submit all of my receipts along with a brief explanation of why a cab wasn't possible. I also was able to get them to refund me the 1,100 ZE1 points that I used for a one-way in lieu of paying, but it took a lot of work to do that.

Quite honestly, Hertz's refund policy is probably the only reason why I still use 24/7.