The men spent twenty seven dollars. The Bellboy took two dollars.
Okay, reverse the scenario. The men first pay 9 dollars each for a thirty dollar room. After realizing that they have to pay thirty dollars, the men decide to pay the bellboy five dollars. The Bellboy takes two, and it all evens out. Thirty dollars for the room, the bellboy takes two. The room gets paid for, and the bellboy gets his money.
9+9+9+5-2=30.
Restructure the original problem.
Each of the three men pay ten dollars. Imagine the manager warps the fiver into the men's pocket which the bellboy invokes his magical thief lord skills to nab two dollars.
10+10+10-5+2=27
27/3 = 9
This works.
The trick is this. The amount of money being tossed about is $27 dollars and $5 dollars; the net amount of money is $32 dollars not $30 as Unknown hero would have you believe. Very Clever.