What I don't understand how it's allowed is that money earned from such ebay sell would go to private pocket instead of the government
I feel like that latter point isn't accentuated enough
First of all -- what? The exact legal authority between the President and Congress here is murky, yes (see https://www.congress.gov/crs-product/RS21900). But it's completely ridiculous to claim that the only criterion for authorization is that someone thinks a person ought to be authorized.
This is unitary executive thinking, grounded in the principle that, because the president is the sole and chief authority and executor of the law, the president may do just about anything in that capacity. It's utter unconstitutional nonsense, no matter what our (openly compromised by lobbyists) Supreme Court justices say.
The latter point is "not accentuated enough" because it's secondary to the primary point, which supersedes it. No the president's whim is not the same as executing the federal laws created by Congress within the framework of the constitution. It a mind-bendingly anti-American, anti-Constitutional line of reasoning on display here.