Tried doing a search on super mojaves for you. Closest I came was a post from April of 2011. $1500. I was thinking they're down to about 1000-1200 now. However, at this point, you're not going to see a lot of super mojaves because other versions create a "cleaner" (read: no grey heads) BEL.
My advice, just go to a trusted breeder to get your snake. They've got a reputation to uphold. If they say it's a mystic, then you ought to be able to trust that it's a mystic. Or are you asking for when you hatch them out?
PS - Good choice on the mystic potions.