If there existed an engine with infinite energy capable of assembling protons, neutrons, and electrons together in the manner you describe, a free market would lose all meaning - markets only appear when there's a scarcity of goods and resources.

No such scarcity could possibly exist with an engine like that: there'd be no meaning in selling the information required to assemble a harrier jet, because its not like you need money for anything - if you need currency to buy something, why not just have the engine assemble it for you? It'll never run out of energy, anyway, so its not like there's any cost associated with it.