Do you want it for a pet, or to breed?
Without a record of the genetics, you can maybe talk them down in price, if you just want it for a pet. Without any information, the snake is, IMHO, by default, "pet quality," even if it appears to be in perfect health.
I actually prefer the normals, but that is a very pretty animal.
If still interested, you can just ask why they are selling. Sometimes people need to sell in a hurry; accidents, job changes, babies, divorces....life happens.