I made a Q&D google spreadsheet to compute championship points values for a variety of scenarios.
You can see it here. I have enabled editing for it, so please be careful to avoid scrambling it up too badly. If you have drastic revisions to make, you should be able to apply them to a copy. Please share your improvement ideas.
Whatever the cutoff turns out to be, this will help a team establish some performance goal(s) for their event(s) without having to strain the imagination too much.