I'd run from this breeder

Advertising teacups & miniature yorkies is a big no no and a major red flag. Reputable breeders do not purposely breed for tinies...they may get one occasionally but never do it on purpose. There is no such thing as a "teacup" or "miniature" yorkie. A Yorkie is a Yorkie - they are a toy breed - the standard says up to 7lbs (although they can get larger than that). There is no Teacup Yorkshire Terrier (or teacup of ANY breed).
Some of those prices are a little rediculous to me as well considering these dogs being bred are not show quality...puppies should not cost considerably more just because they are born tiny.
Also, a breeder can GUESS & make an educated estimate of a yorkie puppy's adult size, but all reputable breeder know that you can never know for sure. So any breeder that tells you a puppy will definitely be a certain weight full grown is lying to you.
Please take you time and search out a reputable breeder. Don't rush just to get one within the next week. You'll most likely be much happier in the long run if you wait for the right breeder and the right puppy.
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~Magnifique Yorkies~
Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs.
Educate yourself and buy from reputable breeders or rescue.