Note that if Wright brothers didn't believe that there was a considerable chance of the plain not crashing, it would be a bad investment to build the plain in the first place. The question is about the cost: does the current state of knowledge support the positive outcome sufficiently to think of designing a plane? To design a plane? To build a plane? To perform an experiment, risking its destruction? To test-pilot a plane, risking one's life?

The same goes for cryonics, here you risk something like 100 bucks a year.