I think what is much more likely is that the regular price for this parking had been increased far too much in the name of political correctness about using public transport and in a recessionary environment people had responded by not booking car parking and either taking public transport or getting their friends to take them to the airport.
Faced with under booked car parks the operators have finally cut the prices but too late to have a big enough impact at this stage of the summer season.
With the weather we are having I personally can't believe that almost every single seat on a plane to the Mediterranean from the UK to the end of the summer school holiday season isn't already sold out although I wouldn't be surprised if the number of flights being operated this season hadn't been cut back significantly before the start of the season due to the recession. However some of the operators like Thomson are very nimble and will lay on say night flights to airports like Palma, Mallorca at short notice to provide extra capacity if all their existing holidays and airline seats to the Mediterranean have now sold out (the short haul planes generally don't fly overnight to the Med but can do to airports that allow 24 hour landings and take offs if the demand is there). There is of course plenty of hotel and apartment ccommodation standing empty down in the Mediterrranean and and especially Spain and Portugal that can be brought in to use at short notice if the demand to go there from customers materialises