A Japanese puzzle

A 2013 Japanese puzzle called "Dollar puzzle" was launched in one
Canadian universities have been able to only 30% of students to answer it correctly,
After this puzzle was considered a measure to determine the IQ of each of the answers, so it was
Consider anyone who has been able to answer correctly that their IQ is
The IQ 120 is often higher than the overall limit.
At first the puzzle may seem simple but it may take minutes and hours to answer it
Correctly, it needs to focus intensely and put probabilities:
Puzzle :
There is a quorum for a bookstore to buy a book worth $ 10
With a $ 100 paper, but fake and unreal, presented "$ 100"
The owner of the shop was falsified and the shop owner did not notice that it was forged
But he was unable to remove it
The restaurant next to it to give it to smaller categories .. The shop owner gave the book and
The rest of the $ 100 ($ 90) per person is the quorum that he took in turn and left.
After half an hour the owner of the restaurant came to the shop owner to return his "$ 100" and
He told him that it was forged. The owner of the bookshop took it without saying a word because it was
His mistake was not to make sure it was real .. and gave the restaurant owner another $ 100 really.
the question :
How much did the man who owned the books shop lose?