First of all, the pup in your avatar is adorable!
To answer your question, there are 2 schools of thought on this topic.
#1- a parti is not up to standard. Since they are not up to the established standard, they should be homed for a lesser price.
#2- some people consider partis as "rare" and will charge an arm and a leg for them.
I disagree with the second school of thought, but not sure I agree with the first. Either way, as long as the breeder did all the health testing on the breeding pair, and the pup checks out, enjoy your puppy!
If they don't even know what health tests to conduct, you're in trouble!