No need to get abusive. These guys just need to learn how to stand up and walk over to their clothes. While walking over, look at your provider in the eyes with a smile of course and see the amazing anticipation they have that you will be giving them their tip up front. While still watching them, start to put your clothes on and see how fast that anticipation turns to concern. The spent 45 minute with you and the fact that they are going to lose a majority of their tip in the last 15 minutes of a session is quite amazing. I do not do this very much, but when I do, they always start the negotiation at that point with a more reasonable value. I only left a session like this once because the massage sucked and at that point, I was not even in the mood to find out if her ST skills were any good.