Depends on lineage, Breeder, generation, Locale, etc. I would expect to pay ~$500 from a reputable breeder (like our forum sponsors). You can certainly find them for less if you look for Hobbyists that have tried, or do, breed. Ask questions, get as much info as possible, especially about parents and lineage. Responsible breeders will have a good deal of background to ensure there is no inbreeding.
You can also sometimes get better prices if you are willing to get a cross. My guy is an Ambilobe x Sambava and I got him for $250. He is as good looking as any chameleon for half the cost. I have no plans to breed them, so I am fine with a cross.