Just to be clear:
This is different than "freelancing" or "contract development". This is more traditional business consulting. You're going in and changing processes and structures more than anything else.
It might be around a specific goal like "make our signups more effective", but you're not just writing some code. You are going in an helping them to change their mindset by incorporating feedback (A/B testing) and new methodologies to run their business better. You get paid so much because the results don't just result in better signups, but in a transformed company at the end.
To do this type of consulting you need extreme credibility. Either a big business win, an ivy league education, or something equally as impressive.