22 year old male looking to remove nevus sebaceous on back of scalp. What surgery is recommended? What is the cost? (Photo)

In tight areas (like the scalp) when excising benign lesions, I often recommend serial excision.  It involves multiple procedures to excise the lesion, the advantage being that it minimizes the scar.  Perhaps discuss this option with your PS in order to minimize any bald patch from the scar.

Nevus sebaceous will continue to grow, so I would recommend surgical excision.  The shape of the nevus is more vertically oriented.  If the nevus is excised in a vertical direction, then you are at risk of the hair parting away from the scar, which will make it noticeable.  If the nevus is excised transversely, then you have a better chance for the scar to be covered by the hair (since your hair would fall over the scar).  This usually is covered by insurance.  If you do not have insurance, you will have to visit different plastic surgeons and decide.  I doubt anyone will give you an estimate on line.  The more important part is to find a plastic surgeon who will do a good job.  Good luck!