In all fairness the Boxster isn't that bad on running costs. I might have only had mine a month but I have all the invoices for any work that's ever been done over the last 9 years (since new). In the last two years (inc servicing and tyres) it cost the previous owner about £5k, having said that the year before it cost him £500. It's just luck of the draw with cars like these. He took it back to Porsche though so with a good indi you would be able to cut a good % off that.
In the past four weeks I've needed a new lambda sensor and handbrake switch. Both easy fixes but still a pain none the less.