I paid almost double that for a 400g mystic less than 2 months ago, from a reputable breeder. The type of mystic/phantom it is will have an effect on how the potion/passion turns out (if that's what you are shooting for).
Also, a phantom x mystic breeding will result in some snakes that look like the super form of either (purple when young, dark silver or dark grey when older, with white markings).