Are you aware that Yorkies can potentially have extensive medical problems? Do you look for breeders who test for those problems and give guarantees based on having tested and made sure their dogs are free of those medical issues ? I would ask about their health guarantees and ask lots of questions about same before buying a dog from them
So sad but true, Yorkies are very popular now, especially the smaller ones are wanted by a lot of people. Many breeders will charge a lot of money for the smaller ones because they can get away with it.
The smaller the estimated size, the more money they will charge,.... will they end up that size or weight? Only time will tell.
I did see one online add for an older championed show Yorky that had already sired many litters. The breeder wanted $10,000 for him. I don't know the situation of the one you saw for $9,000, but if the breeder has gone to a lot of shows to champion their dog, they may consider that a good price for the time,vet bills,lab tests,traveling and show expenditures to have gotten him there? That I can only guess at.
Certainly not a reasonable price for a pet!
Even the best breeder who does it only for the love of the breed, has considerable expense going into each and every puppy. Its not just loving Yorkies and breeding two dogs together.
The local pet store asks $2000 + for the dog and accessories and first weeks food for a pup less that 3 months old. Of course they no longer sell AKC dogs there.
Make sure you ask about the medical tests they have done, if they don't test, or seem unaware of any medical issues Yorkies as a breed do have, then run the other way! Don't buy a dog from this kind of breeder!
The medical problems I can list off of the top of my head are Liver Shunt,(more than one kind, usually born with them, not always obvious to those who don't know about them) This causes the liver not to function properly to filter out normal and natural toxins in the body, can lead to constant illness and death. Legg Perths, a hip problem usually requireing surgery to correct, luxating pattelas are a knee problem that they can be born with or can occurr because of injury to the knee from jumping off of furniture,etc due to their very active nature. Collasping Trachea which causes the dog not to be able to breath properly, sounds like they are sneezing backwards or coughing, happens when they get excited or over exerted. They can have heart and eye problems , so ask about those too! Talk to your vet and ask them about any potential problems they know about with the breed and do they know of someone who has medically sound dogs whom they would trust to buy a dog from?
Do lots of research, don't just fall in love with pretty pictures on the internet