A good problem to have

I don't know if I'm asking a question or if I just bragging on my crew, but lately everyone that I invite on my boat tends to give me way more cash than they should. It is actually kinda awkward when someone hands me a $20 and only took a 10 minute set.

We had a kiddo 2 years ago, so for the previous 3 seasons most of my riding was drop the boat in, ride and take it out. This year we have been inviting people out and I have watched my monthly gas bill drop to zero.

What do you guys do (besides invite him/her out next time) when someone is way too generous with gas money? Especially when all they take is a surf sesh or it is a beginner that is riding with no weight.