The US certainly didn't stay out of the war because they thought they would make money. There was no civilian backing at all, and they was no reason at all to enter the war (No treaties broken, etc). Also, the US didn't make bank from world war 2 at all. First, there was the lend-lease program
https://en.wikipedia.org/wiki/Lend-Lease (Note that 50 billion was given out and an incredibly small sum was ever paid back, a couple of billion)
And then there's the Marshall Plan
https://en.wikipedia.org/wiki/Marshall_Plan (Note that 12 billion of aid was given out to help reconstruct Western Europe and only 1.2 billion of this was loans.)
And on top of that, the portion you quoted means that is how much information they gained from the German research they took, not money paid. One can argue that the information they gained was used during the reconstruction of Western Europe, so West Germany and other countries benefited from it.
Also, laws exist to prevent cartels and monopolies in the US.