Its possible 100x may be an underestimate
What's a "bug" during requirements stage? It is something where the requirements are found to be in error or missing something simple, and corrected before a single line of code is written. So the additional man hours of effort required to fix it is approximately nil. Any effort post-production will be infinitely more than that.
You may ask, what if something missing during requirements is caught but it adds 50 hours of work when you do get to coding? I'd argue leaving that out couldn't be classified as a "bug", because if you added it post-production you'd never call something like that a bugfix. You'd call it an enhancement or new feature. If you were doing the work for a customer you'd bill it as a change request.