From my own experience I have to agree with the post above.
Once a very decent guy left money on the table and I didnt bother to pick it up and count it for some reason.
So I proceed with the full hour worth of service, cum twice etc. Also doing a full body to body erotic massage in between, so in the end I pick up the money and see that its only a half hour fee.
Well, apparently he couldnt get enough cash together for 1 hour appointment, but failed to inform me he only wanted/ could afford half an hour. He just left the cash on the table and stupid me assumed that we are going ahead as previously arranged (1 hour booking).. When I confronted him angrily to ask why didnt he stop me when it was clear we were well over half hour time, he replied that he got lost in the moment and got carried away.
Grrrr what a fucker!
But lesson learned though. Count upfront, Always in front of them, as if you take it away and find it short how would you prove it .
Good luck!