Like your West Highland White, Yorkshire Terriers are considered to be one of the low shedding breeds. All dogs shed, but some shed less than others.
Please note that people may claim that Yorkshire Terriers are hypoallergenic, but no dog is truly hypoallergenic. It depends upon the specific allergies since people can be allergic to hair, to dander, to saliva, or the different grass pollens or dust that is carried inside on the hair.
As far as cost, it is important to check with some reputable breeders to find out how much they are asking for a puppy. Pet quality puppies are often sold for a lower cost than show quality or pick of the litter, so don't forget to clarify what you are looking for. You could also check with a breed club.
For your information, here's a list of the low-shedding dog breeds:
Bouvier des Flandres
Chinese Crested Dog
Portuguese Water Dog
Soft-coated Wheaten Terrier
West Highland White Terrier
Sincerely Zena & Zippy