Yak cows eat approximately 25%, or 1/4 as much food as a beef cow. There are a number of reasons why. They are about half the weight of a beef cow. They don't need near the food to maintain body heat...
They cost 100,000 per year.
A yak typically weighs around 700 to 800 lbs.
257 to 270 days
they normally cost about $12 on eBay for a yak low profile and about $25 for metal cores if you find a good deal