I'd say write the couple a letter and tell them what you told us. What do you have to lose at this point? But in the end, that will just take up more of your time.
They probably know that "the squeaky wheel gets the grease" most of the time, so they're chronic complainers and takers. I agree with the others. Good riddance. You know your value even if they don't. To heck with 'em!