Puzzle

My father gave me the following puzzle:

One day, 3 men went to stay in a hotel. The hotel room was $30, so they paid $10 each. Later, the hotel manager found that there was a special offer and it was actually $25. He gave the bellboy $5 and told him to return the money. But the bellboy kept $2 for himself and gave $1 each to the 3 men.

The bellboy thought: Each person paid $9, total $27. Plus the $2 he kept became $29. As the 3 men first paid $30, where was the missing $1?

What do you think? Please put it in the comment box below this quiz. Thank You.