I'm not really an expert, but I would assume that when you make so much money that offshore is a good option, then I think you wouldn't need to ask those questions in GFY.
Anyways, I think they cost starting from 2,000usd setup.
Plus yearly fees and fees for the company that takes care of your company&account
Those costs added to the cost of the risk that you're (probably) illegally avoiding taxes in your country ...
