Every time something breaks, check to see which of the tests would have caught it. If only one test would have caught it, then you can summarize that test has s

Every time something breaks, check to see which of the tests would have caught it. If only one test would have caught it, then you can summarize that test has some importance. If 24 of the tests would have, then each one individually has less value when the others are present. Do that for a while. If your goal is to have absolute zero customer breakage ever, then you're just going to have to do the combinatorial tests no matter what or literally never release anything because that's what you decided to optimize for.