It's an allegory. Mr. Myne's machine represents the increased efficiency of future industrial capital. The magical machine is all the advancements of agriculture wrapped up in one black box, and completely automated to remove wages from the equation.
In the future, when robots can make everything you would ever need more efficiently than you can do it yourself, what can you possibly do to pay the owners of the robots for the things the robots make?
There aren't many options. You can own your own robots. You can do something the robot owners want that can't be done by robots. You can abolish individual robot ownership. Whatever you do, you have to think about what happens when producers and consumers are separated by an economic wall, when there's nothing that you can do that a robot cannot do better. Where you have nothing to bring to the market that anyone else wants to buy. It's not just people deciding not to pay. At some point they won't even be able to pay.
Most of the developed world already has access to potable water for very low prices.
Does this machine need to be one per person or can it be scaled to have one giant machine feeding a bunch of people?
If the machine can be taken apart and replicated then Mr. Myrne is going to be sol.