I bought a yorkie with CH parents and didn't spend near 4000. I know that you can buy a nice yorkie with nice lines behind it for alot less than that. I would mostly stay away from people that are using "special" terms like teacup, rare, etc.... to sell their dogs for more.
I also like to think that it is worth it to pay a little more and get what you want from a good reputable breeder, you are not just buying a dog, but begining a realtionship that can last the durration of the dogs life, a good breeder will give you support, and answer your questions long after the sale is final. You also are paying for the breeder's hard work, and knowledge, good ethics are worth their weight in gold IMO.
A normal price for a pet seems to range between 800-2000 roughly(kind of a big range but I know people that have paid more and less than that
).