--> OK - does this guy think that I went "Ohhhhh, I see. Their stuff will now go in the stack for people whose returns need to come out with refunds. Also, note to self: Don't charge them; after all, they could have done it themselves. <---
I like that. I think in the future if someone says they don't want to pay I'll tell them I'll just put their return into the "refund" stack.
As for how to charge those who could have done the return themselves, I think you should tell them you decided to forego being a brain surgeon and chose to go into tax preparation. So since you "couild have" been a brain surgeon, you'll charge them brain surgeon rates for preparing their return.