Yorkie's do not eat much food, so it is easy to buy A high quality pet food, it goes A long way . Keep in ming that the benifits of providing them A high quality food is worth the extra money in the long run. The have fewer health issues, and can even live longer life spans .
I do not know what is expensive to you, but , i feed my Puppy A kibble by Nature, it is Organic. She also eats the canned food by Nature. I give her that in the eveings and leave the kibble out for her with fresh water.
Always start out slowly when you switch foods. The canned food I give Suzi does not upset her tummy.
I honestly do not know of any cheap high quality dog foods out there. you Do get what you pay for.
