It's really not. Start-ups routinely fail to generate value and engineers get hired by such companies all the time. All that is needed is the belief it's possible the value will be higher. The reality doesn't need to match the belief.

But then the engineers at the successful company can't capture a significant amount of the value that company makes, because the rest of it has to go back to investors to make up for all the other companies they funded that 'overpaid' engineers and failed.