There is a thread from somebody who really doesn't know the difference and trying to defend their breeding for tinies. Rather than respond to that one, I wanted to write my own based on my own experience as a show breeder.
Any breeding I do, I am trying to hopefully produce my next show dog. It doesn't always work out that way so puppies in a litter that in my opinion and in the opinion of my mentors, that do not look like they are something I would want for the show rings, I sell for pet. I do not ship, and rigorous interviews happen before a sale.
These are healthy happy little dogs, very good quality Yorkies. Some can be undersized, what bad sellers sell as 'teacups', or might be larger, oversized and can be sold for pet, as a larger yorkie. All are non breeding contracts or already spayed or neutered if I decide after they are 6 months old not to keep it in my breeding program. Yes, I have had small ones that were relatively normal size at birth but will be less than 5 lbs full size. They are not runts, they are small. As I do know that very often small ones can have health issues, I do not consider a pet home for a tiny one until it is close to a year old, health testing that can be done is done and spay/neuter is done.
I don't sell it but keep it myself if there is any question about its health.
I do not sell it for high prices if eventually I do look for a pet home for it. And the interviewing etc, I do is rigorous as someone buying a pet has to understand the care and time and possible expense of having a small one. Dogs are not accessories. The worst possible thing you can do is think you can carry them around in a bag and show them off like a new bracelet. They are way too delicate.
The Yorkshire Terrier Club of America has this information on their site about teacups.
Yorkshire Terrier Club of America (Awards)
THE REAL WORLD OF SHOWING DOGS
I now have finished about 10 champions in Canada. I show my own dogs I do not have a handler. I am fortunate that many shows are within driving distance and I am likely away from home less hours for a show than many of you are gone when you are in a mall doing shopping etc.
It is not true that show breeders are gone all weekend going from showto show to show. Professional handlers are but not breeder/owner/handler show breeders. We pick and choose what shows we will go to and also what ones we can afford.
If we do have a weekend we are away, we choose carefully who will be dog sitting for us. Indeed, many show breeders have family and friends who take on this job.
We support ourselves by working our own jobs, not off the backs of our dogs. We again have the type of jobs that we can work from home, have spouses that earn a lot of the income while some of us have part time jobs, some own businesses, some can take time away from jobs when necessary, some have jobs with bosses that have no problem with them taking a dog to work with them if necessary, all of which lets us pursue our hobby without living off our dogs. If I had to live off my dogs, I would not breed anymore.
A reputable breeder would never purposely breed for tiny. I do not ever entertain the idea of using a bitch or stud for that matter for breeding less than 5 lbs. At least one is a champion, and about 75% or more of the pedigree are champions, including my own dogs in that pedigree.
If you want to buy a show dog, go to a show breeder not someone who claims to have champions in their pedigree. Go to a seasoned show breeder meaning someone who has finished several champions OF THEIR OWN BREEDING, not just bought off of a show breeder who they either were not truthful with about what they wanted to do or the show breeder didn't care who they sold to and there are some around unfortunately, which has put some very nice kennel names in the wrong hands as those very nice kennels names got scammed by someone not honouring a contract and should not have been trusted.
Any litter I produce, might have a show dog, possibly two. Other puppies in that litter, might be a pet quality. All puppies in that litter has the same pedigree but notice some are show quality or might be, some are not.
I cannot fathom any excuse for purposely breeding for tinies or breeding a purebred without the breed standard in mind for any mating. Indeed with any mating I do, what I hope for, is not what I always get. Breeding different sizes to produce a size you think you will get never works. From what I have been told, inbreeding tends to produce tiny more often than not although again, not always and you run the risk of bad genes doubling up to produce a problem.
There are too many factors in genetics involved to be absolutely certain what you will get as a result of any mating.
The best justice you can do to the Yorkie or any purebreed breed you are interested in is to work with longtime show breeders to mentor you, breed to the breed standard including size and colour, rather than breeding a commodity to sell to a pet market.