Where I live, one liter of soy milk costs about $1. This might not seem like much, but considering that soy beans are so insanely cheap themselves, and most of the soy milk is actually just added water (only 8% is actual soy, the rest is water), why is the price so high relative to the ingredients? It seems like it’d cost almost nothing to make. I know that the supermarket has overhead, but that is similar for all products that they have and there’s plenty of stuff that costs almost nothing. Is it just a ripoff to exploit health conscious consumers, like some organic foods are?
I think it’s a safe bet that an even higher percentage of Coca Cola is “just added water”.
There are probably some costs involved that you’re not aware of, and that you didn’t list in your post, but the main answer is: Because that’s what people are willing to pay.
You do realize the supermarket doesn’t just snap their fingers and soy beans turn into soy milk, right? I’m not saying there’s not a large profit margin, but you don’t appear to have considered the cost of production at all.
And with a limited number of producers, the transport costs of a heavy product must be a large percentage of the price. Isn’t whole milk also around the same price?
If you do a Google search, you can find fairly simple recipes for making soy milk. So why not try it yourself, paying attention to the cost of the soy you start with. Is the cost and trouble more or less than that of packaged soy milk?
Running a factory to produce soy milk costs money. Transporting it to a distributor and then to your local supermarket costs money, and everyone along the way needs to get paid.
You might want to shop around and see if you can get it at a bulk retailer like Costco or Walmart/Sams Club and I bet you can beat the price of a local grocery store. I would say that a dollar a liter is actually pretty cheap considering all the costs involved.
I would say a buck a liter* just coincidentally happens *to be the median price for cow milk. Can’t be any connection regardless of relative production costs, of course. 
Technically, we refer to people who buy organic food for health reasons as “idiots” (the science does not support the notion that organic is healthier – the opposite, in fact), but generally speaking, its higher price is mostly because of the much lower yields of organic crops per acre, not as a gouging mechanism. There will be some exceptions, of course.
Note that the supermarket will gladly sell you a liter of tap water for a buck, without even going to the effort of adding cooked soy pulp.
But they do “purify” it for you :dubious:, and they’ll even put a famous brand name on the bottle.
Transportation costs and supermarket markup also apply to raw soybeans. I’d think that the additional cost is mostly due to processing, labor, and packaging. Advertising, too, if it’s a known brand.
I didn’t know that. I’ll be sure to look into it.
But my point is broader: when a new product is added to a spectrum, it tends to be priced similarly to equivalent products for many reasons, regardless of relative cost or profits, at least initially. So cow milk costs, say, 40 cents a liter to put on a grocery shelf while soy milk costs 8 cents? Pricing it more or less the same as the accepted original will help ensure consumer acceptance and confidence. If soy milk were half the price, there would be twice the suspicion that there had to be something wrong with it. (And charging a lot more on the basis that it’s a “premium” product would doom it to a niche.)
Designer tap water is usually priced the same as sodas, which are closer to a buck-fifty a liter, BTW.
Soy milk isn’t powdered soybeans dissolved in water. Making soy milk involves soaking the dried beans for 10+ hours, grinding it, filtering out the pulp, then boiling it. At least that’s how you make it at home, and I don’t see how it can be very different in a factory. It’s not exactly a trivial process.
My guess is that if there was more demand it would be cheaper.
Think of it this way, if you made a pie it would take X amount of dollars and X amount of time. To make two pies, it only adds in a bit more money and time.