Payments in exchange for regular business which would have been engaged in anyway would seem not to apply, although there's disturbing room for corruption there.

"No title of nobility shall be granted by the United States: and no person holding any office of profit or trust under them, shall, without the consent of the Congress, accept of any present, emolument, office, or title, of any kind whatever, from any king, prince, or foreign state." [1]

Add to that:

- The lack of case law or Congressional guidance;

- George Washington receiving and accepting "two gifts from officials of the French government" without asking for nor receiving any Congressional consent [2]; and

- Almost every Founding Father from the South operating their plantations while in public service.

I think it's safe to say (at least as a non-Constitutional scholar) that this clause is far from definitive on anything. Please note that I am not defending Trump's behavior nor saying this clause cannot be interpreted to apply. I'm saying we cannot comment on this with any reasonable degree of certainty.

[1] https://en.wikipedia.org/wiki/Title_of_Nobility_Clause

[2] http://www.nytimes.com/roomfordebate/2016/11/17/would-trumps...

What nation, looking to create a favorable deal of some kind with the US, would allow a Trump project to languish in frustrating red tape -- or allow a Trump project to lose out to a competitor in cases where the government is the decision-maker? What would the informal Trumpian chatter be like around that international negotiating table?

Whether it does or not is ultimately something that'll have to be decided in court.