If you say a calamity will befall me, and ask me to pay to protect against it, the burden is on you to (a) prove the calamity is likely in all its details, (b) the cost of the protection is worth it in the sense the protection is likely to do the job asked of it, and (c) that no other forms of cheaper effective protection exists.
If you cannot do all three, then I am under no obligation to heed you. Showing only one element is insufficient to compel my action. That is, showing only that the calamity is likely isn’t enough.
For instance, if you convince me, based on some set of evidence, a moon-sized asteroid will ram into the earth in two years, but then offer to sell me at high price a magic spell book which, when used, might dissuade the asteroid, then I will not buy. Even if I agree the world will end.