I agree with everyone else, this individual is just trying to 'make money'. "Yellow" labs come in such light shades occasionally as to be considered 'buff'...but they still fall under "Yellow" category.
However, if this dog is truly "white," it could be an albino which can happen. It would be basically white with pink skin -- eyes wouldn't be as dark and quite possibly red. It would still not make the dog 'rare' or 'valuable'. It's a major fault and will likely have health problems throughout the rest of its life :(
hth,
toodles