How much to pay a skilled intern?

We pay an hourly equivalent that is about 40-50% of what a starting full-time salary would be at the same position, and have never had problems with enough (quality) applicants.

However: - We are in the midwest, without much competition. - We are in a college town where there is mandatory internships as part of the CS program.

So YMMV.

I'd shoot for about 80% of the starting salary you'd pay if they were a new full time employee just getting out of college.