Those are beautiful Bettas! However, I don't want to disapoint you on something I feel I should mention. White Bettas are the "normal" original color of bettas. They are mostly white in the country of origin. They were breed to have colors for "flashier" fights.
I am just saying this so you don't run the risk of getting "ripped off". Not that I wouldn't want them myself and I do!!! Just be careful in believing the "hype" the breeder may be giving you. They could be "imported".
My father was a Betta breeder. We'd have tanks everywhere! However, I will agree that the all white ones were a "rarity" to have.