Erik M. Jensen, Coleman P. Burke Professor Emeritus of Law of Case Western Reserve University, wrote a journal article published in the Elon Law Review titled the Foreign Emoluments Clause. That article examines the definition of emoluments, the history of the emoluments clause, and debate as to whether the clause applies to Trump and his businesses.  He sums up the problem of the Trump Hotels as follows:

[S]uppose a foreign diplomat is paying the same rate as the guest in the next room, but he is occupying a room that would otherwise have been empty for the night.Or suppose the diplomat, in selecting sleeping quarters, chooses an otherwise unoccupied luxury suite over an otherwise unoccupied, but substantially less expensive, room. In those cases, whatever is paid for the room, or the extra that is paid for the luxury suite, is mostly gravy for the hotel’s owners. Why is that not a potential problem under the Foreign Emoluments Clause (at least if we assume that the presidency is an “office of profit or trust”)? By any standard, the arrangement is unseemly, and by its terms the clause has no de minimis exception.