Species with small home ranges and relatively dense populations, like ball pythons, tolerate in-breeding very well, I guess that must be how breeders produce so many color morphs. Indigos are at the opposite end of the spectrum. They have really large home ranges and sparse populations, but do not tolerate in-breeding very well. Thus, captive breeding of a limited gene pool is producing problems of kink tails, dwarfism, split ventrals.
I would think that selling kink tailed individuals, even though honestly advertised as such, would be a poor business practice. You are telling the world that the potential for this particular problem runs in your collection of breeders.