$500 so far is the most I've popped for, several times. I'm currently in the start up phase of a SD/SB thing with $500 per long session being the agreement. This is really a bit out of my financial range but from the one time BCD with this UTR lady being one of the best experiences of my life I will continue. Just not as often as I would like.
On another note a provider I've helped a bit here and there over several months has run up quite a tab. It was agreed up front that it was not loans but would be paid back in services. We are currently coordinating a weekender in my RV at some out of the way camp ground. This will settle her tab, I will be in an environment I love, and likely will need a paramedic to haul me away.