I don't pretend to know how this could be done or even if its possible to do. But if non-donating members could see all the threads that the donating members could see, but get a message when they try to open it saying "this off topic thread is for donating members only. To donate go to .....etc. etc." They would get the same list of threads as a donating member does when they click the "today's posts" button, they just wouldn't be able to open every thread.Then instead of taking our word for it that its the best $10 they'll spend this year they'll actually get an idea of what they're missing out on. As it stands most folks are befuddled by the complete disappearance of an off topic thread they unwittingly started. If they saw their thread, clicked on it and got the above message they'd be on their own path to enlightenment. No more "Hey what happened to my thread", threads.
Like I said, not sure if its possible, just putt'n it out there.