You had a good idea, but your premises are wrong. Notably, your insurance is "tied to [your] pension". Assuming an average retirement age of 65 and that people will live to be 70 (to match your numbers), that's two colonoscopies per person, for a cost of $2,400,000 to (hopefully) prevent treatment for 70 colon cancers, so it has to cost less than $35,000 for it to make sense.

On the other hand, even that premise is wrong. If you don't check for it, you don't know you have it until you're months from certain death. It's probably a lot cheaper to pay for palliative care for those few months than actual cancer treatment for what (the patient would hope) would be a lot longer.