I'm not sure it's possible for factory farms to change, especially when raising animals. If you talk to someone who raises animals in a sustainable way (if you don't personally know a farmer, read Joel Salatin), they will tell you there is absolutely an upper limit to what can be produced sustainably. I purchase all of the meat my family eats from a local farmer (who only sells directly to consumers) and he said while he could easily double the number of customers, he wouldn't be able to maintain the same practices (this includes everything to what the animals eat--grass only in the case of ruminants--to where the animals actually lived--all are pastured in the style popularized by Salatin).
I could be old-fashioned and myopic, though. Maybe someone can figure out a way to have the best of both worlds.
Regarding cost, I no longer worry about the amount of money my family spends on groceries. Yes, we spend $5/pound for beef, and $2.50/pound for chicken, but this is stuff we are putting in our bodies--it's what keeps us alive. I feel that price shouldn't be the driving factor in what we eat.