When you say “biggest profit,” do you mean the most amount of dollars per pound of the stuff being cranked out?
In that case, I’ll go with Schnitte and Argon 38.
IMHO, answers like moon rocks fail because by definition, moondust cannot be synthesized.
If by “biggest profit,” you mean total revenue per year from selling an unlimited supply of the stuff, the question becomes more interesting.
Certainly, Argon 38 has a much more limited demand than say, oil.
Put another way, the total world consumption of oil, measured in dollars, far exceeds the same for Argon 38.
I’m not an economist, but I’m gonna guess “oil,” because I can’t think of any other substance that commands so much of the world’s attention.
At $30/bbl, I would guess that total world oil consumption is on the order of $1 trillion/year.
If you could generate an unlimited supply of oil with no marginal cost, you could get a big piece of that trillion dollars, although as other posters have pointed out, adding a lot of oil to the market would surely cause the price to go down.
I’m not an economist, but I imagine that if you charged $1/bbl you could drive have the entire market to yourself, although you could not maintain monopoly prices, since other oil producers could go back online if you raised your prices too high.
At $1/bbl, world oil consumption would increase dramatically (a lot more SUVs?). Supposing it increases to 40,000,000,000 bbl/year, you’ll make $40 billion per year.
Of course, if your machines can crank out manufactured goods, then I suspect you could make even more money, although it becomes harder to guess how your products would be received by the market. (Would people buy your cigarettes instead of Marlboros? How would governments tax your products?)
Another question is how broad or narrow the class of goods you could make with your machine? Just one kind of car or chip? Or many?
http://www.bea.doc.gov/bea/gpxind-d.htm
This site might give some insight.
Unsurprisingly, “electronic equipment” seems to be an area where demand is going up. It looks like the total domestic product (in 1994) in that category was $130 billion (for the U.S. alone).
No doubt consumption is much higher today.
Also, I suspect that profit margins are slimmer for manufactured goods than for oil. Perhaps undercutting your competitors by 50% would be enough to take over the world market.