How much is it to remove a nevus becker? How many sessions will it take? Will it actually work?

IT can take many treatments 6-10 and often they still remain or come back. i suggest going to a laser expert for a formal evaluation as there are no photos online here for us to give an opinion.  Best, Dr. Emer.

They can be improved and sometimes removed depending on characteristics and location. Would need to see a photo to advise properly though. 

Becker's naves is notoriously difficult to treat as it has many element including excessive pigmentation, hair growth, smooth muscle excess and even excessive acne glands. Laser can only target specific areas of Becker's naevi- the easiest to treat is excessive hair growth. Other elements of this birth mark are very hard to treat as the structures lie deep in the skin's surface- beyond the SAFE reach of lasers. I try to convince my patients NOT to treat Becker's, however a test patch can be conducted. All the best, Dr Davin LimLaser DermatologistBRISBANE, Australia.