I think the point was to demonstrate what a rip off car parking at airports is, especially BHX. I've been on the receiving end of short stay fees and it would be cheaper to park a 747 than stay over in the drop off area.
I'm trying to remember whether they still charge for dropping off? Last time I used the airport was March, and I was more bothered about making my flight - think the taxi driver did still have to pay £1?
Apart from that, airport parking is like any other service in the travel trade - book early and pay a reasonable rate, or book late and pay a fortune.