How much a dermatologist, who owns their own practice, make?

It would depend on so many things -- how many clients they had, how many employees, cost of insurance, taxes, rent for the offices, medical equipment, etc. At the beginning of their practice, they wouldn't make much at all. But once they were well established, a dermatologist with an ordinary office and an average range of clients and services might make $100,000 or so. A dermatologist with an extremely popular and high end office would of course make much more.