In addition to the reasons already listed, milk sold raw for consumption (as opposed to pre-pasteurization conventional milk) is not subsidized by the government (i.e. your tax dollars). The subsidization of feed crops (corn, soy, etc.) is a huge part of why conventional milk is so "cheap", the true costs are hidden from the consumer. There's also the cartel-like system of milk processors who have a virtual strangle hold on dairy farmers, often they pay the farmers less than it actually costs to produce the milk and the government pays the farmers the difference. So, comparing the price of raw milk that is produced outside of that system to the price of conventional or processed organic milk in a grocery store is very deceiving. That doesn't help if you simply can't afford it, but there is a factor of sticker shock when switching one's food buying away from typical grocery-store fare. A shift in attitude about the true value of real food is often in order.
BTW, in my state, the legal raw milk available to purchase in stores is $16+/gallon, and since I have a cow and know how much it costs to feed her quality, organic stuff and maintain adequate pasture in this climate, not to mention the level of testing and regulation, that price doesn't seem out of line to me at all.