Others made the very good point that actually the mismarked dogs can be the most special as they are that bit different! I really like cavaliers with half a mask, for example -- very cute and different and rare! I have what is called a heavily blanketed tricolour -- she is nearly black on her body, with only a white ruff around her neck and a white spot on her behind. Those would be very undesireable markings in a show dog (though would not necessarily mean a dog couldn't be shown if other far more important elements were very good! Coat patterns are about the least important element ).

If this mismarked puppy is 20 weeks old,I wouldn't be surprised if the breeder would consider a reduction to allow it to a good home.Sometimes small breeders are limited for space and especially if another litter is due,they may be anxious to rehome the older puppy.
However,I would find the breeder's sales pitch offputting.
Good point, and good point. I think talking about 'discounts' has made this puppy sound as if it's a bit of a problem.... It just kind of ends up sounding like a backyard breeder so I guess that is what triggers some of the concern shown here. But of course we're just getting a summary of what she has said and all may be very honest and straighforward and generous.

Sins is right though; don't take any puppy that you will not be happy with for the next decade+. For some a cosmetic issue is a problem; for others, it isn't.