This may seem like a lot of money to pay for a puppy, but the price paid often reflects the quality of the breeder. Potential owners should be extremely wary of breeders offering Shih Tzu puppies at very low prices. This is likely to indicate careless or over-breeding on the part of the breeder, and a high risk that there will be health issues present that could present many problems for you and your puppy.
As Shih Tzus are such a popular breed, there are many breeders registered with the American Kennel Club. While this in itself doesn't guarantee a healthy puppy, it's much more likely that you will be dealing with a reputable breeder who will have an interest in ensuring that your puppy is as healthy and well-socialized as possible before you take her home. After all, their reputation as breeders depends upon keeping their dogs healthy and their buyers happy.