Thanks for a heads up, just booked my parking in P3 for Xmas holidays.
The odd thing is that 8 days parking booked on Finavia webpage costs 56€ (with current discount from 72€) but mobile booking is 58€ @:-)
I have a 17 days ZA trip in January/February coming up and parking in P3 is only 75€ if purchased now, very good value IMHO - and you can even get AY+ points for your parking!