Carin, Just a silly thought. Sun cream is much cheaper in the US than in Corfu. So much so, that I try to pack enough to last us the whole summer.
Re. presents, for those you have to buy for, I stick to small gifts, like calendars with pictures of Greece / Corfu, small candles etc. You can easily get small gifts for people without spending much at all.
If you are not a big drinker, I think you may well find Corfu a little cheaper than the US. Four of us can have a great meal for E60 or there abouts, add on drinks and it goes up a good bit. I would estimate around $20 per person for dinner if you have a main course and share 2 or 3 starters. Add about $5 if you also want dessert. Hope this gives you a bit of an idea.
In the day, we stick mainly to drinks frrom the supermarket apart from bottled water and the odd diet coke. A can of pop in the supermarket cost 55c last summer, so I would say that is more expensive than a US supermarket but cheaper than a drink machine in a shopping mall etc.
Hope you have a lovely time,