Cusian, during the NBA combine, Richardson stated that he would only remain in the draft if he was going to be a first rounder. Look it up--there's an article on Syracuse.com where you can find the quote.
That's not me imposing any benchmark upon him, that's his stated line of demarcation.
I posted a thread stating, "uh oh--I'm seeing some sources of data that have him outside that range." It isn't me feeling that he needs to justify to me or anybody else that he went pro. It isn't applying a framework of "right" or "wrong." It is objectively looking at where he is projected [the key word being PROJECTED] in some [operative word: SOME] coverage of the NBA draft.
So yes, to put it in your terms, if he goes #10 I'm sure he'd feel that his decision to turn pro was justified, based upon the criteria that he himself stated. If he goes #40--again, borrowing from your example--then I doubt he would. Because being drafted higher in the draft means more money. It means near automatically making a roster. It means having a guaranteed contract [which can be earned as a 2nd round pick or even as a UFA I suppose, but that is no sure thing either way]. And the higher he goes, the more his salary increases.
Since he's a professional basketball prospect, I assume that those things are important to him, and don't need to be justified nor validated by me. His professional goal is to make money playing a game that he's good at. And I'm sure once he gets drafted, he'll have other professional goals. But I can't envision under any circumstances that he'd feel satisfied with being a second round pick, and getting a lot less money and / or possibly not making an opening day roster if he gets drafted by a team with lots of guaranteed contracts that doesn't have room for him.
I labelled this business about "right" or "wrong" as your baggage, because you are inserting a bunch of stuff into the discussion that doesn't belong. I'm sure there are threads criticizing his decision to go pro--this isn't one of them.