Andreas the Alchemist on Youtube has a scaled up machine that supposed can do about a gallon of nitric acid every 24 hours, somewhere near the fuming nitric concentration (at the cost of something insane like 5kW power consumption).
120 kwh * $0.13/kwh = $15.60/gallon near where I live. That's not too bad in and of itself.
I wish he would publish plans for his machine, or someone would offer to build them. Wouldn't matter if it cost five times as much as retail, to be able to make fertilizer and prague salt with nothing but air and self-sufficient power would be a god-send.
Though, I gotta say that his fucking power supply gives me the heebie-jeebies just watching on Youtube. Electrical is one thing, but I know better than to look at high-voltage cross-eyed...