It can be as cheap or costly as you want to make it, we did find it expensive last year but we ate every single meal out . However there are 2 very good and well stocked supermarkets so you can self cater very easily if you wish, just check the apartment facilities are "up to it".
Regarding car hire, i cant say because i always use the local buses or the boats which i find more fun, but i guess it does limit where you can go.
Hope this helps a bit
Phyll

hi phyll thanks for info we also eat out every night and snack during day but i was just wondering if the crisis on mainland greece has bumped up the prices of drinks and meals what would you say was exspensive . i was getting a good meal in sidari last year for about 20 euro for two and drinks . cheers

I think it depends what you eat ! I didnt find anywhere as cheap as that but we really did "pig out" so i am sure it can be done, i am going back next year and already plan to eat less The one thing that is expensive are the cocktails, about a fiver for one and they are so lovely so just slip down ! hence the problem with having too many.
personally i love the place so much that i would put myself on "rations" just to be there
Phyll