Veterinarian here.
Just thought I'd mention that milk is generally not subsidized. Quite the opposite: there are wholesale price supports to keep dairies in business. Conventional milk sells wholesale for $11-$14/cwt, approx. 8 gal. The typical dairy barely breaks even. The difference between the wholesale price and the store price is mostly taken by the distributor, e.g. Dean's. Aldi milk is cheaper than the rest because it is a loss leader for the store. That's why there's a limit on milk purchases at the low price. Organic milk and rBST-free milk sells for a higher price.
Personally, I dislike rBST for two reasons. One, I don't think it's right to take cattle (Holsteins) that already over-produce milk and make them produce more. Two, it's counterproductive because it creates oversupply in an environment of already depressed milk prices. It only benefits the drug maker (Elanco) in my opinion. So I recommend the rBST-free product because I think it's better for everyone involved.
The majority of the milk is used to make pizza. The fraction of liquid milk going to consumer drinkable product has been declining for a long time. Lots of dairies have a single customer, such as a cheese or a yogurt company.
There is a lot of variation in dairies regarding cleanliness but most dairies are pretty conscientious. Holstein cattle are hungry all the time because they produce so much milk, so they are not usually out on pasture. They are eating high-energy food and hanging around a barn. So good dairies have automated cleaning the barn so that they are not standing in much muck. If you put them on pasture, they'd all be hanging around in the muck near the feed trough anyway. The lower-yield cattle take much more time to rest and so they are better for pasture.
Dairy cattle perform an important service recycling the tailings from several industries. Beet pulp (sugar), distiller's grains (ethanol) and peanut hulls are all mixed with corn silage to make feed. One of the big jobs dairy vets do is keeping tabs on these incoming food sources and making sure they get blended in a healthy way. The outputs are milk and manure, and the manure goes for organic farming. All in all, it's not a bad industry.