Brain Teaser?

Okay. I am bored so here’s an old brain teaser question for everyone.
3 guys went to the hotel to meet their girls. They met the receptionist who charged them 10 dollars per night for each person. They quickly settled their bills and head off to their rooms. Later the receptionist found out that the room rate was wrong. It was suppose to be 25 dollars for the 3 rooms. But this receptionist is tricky, so he took away 2 dollars for himself and return a dollar each to the 3 guests.
Now,

10dollars – 1 dollar =9 dollars , so each of the guests effectively paid 9 dollars for their rooms.
9 dollars times 3= 27 dollars, which is the total amount paid by the 3 guests for their rooms .

NOw, 27 dollars + 2 dollars ( stole by receptionist)=29 dollars, and where does the 1 dollar gone to since , initially the 3 rooms costs 30 dollars.