The overwhelming majority of people don't pay 15.3%, currently they pay 5.65%. Last time I checked 5.65% is less than 9%. Then people will be paying an additional 9% on virtually everything they buy. An average family of 4 earning the median family income of $49,500 will probably see their taxes more than double under Cain's plan.
This is a fight between the seen and the unseen. As an employee it only appears that you pay half. This is a typical money illusion of the left.
Your employer pays the other half, but pays it regardless of whether it goes to you or to the government. In other words you pay the whole thing.
Just like you pay corporate taxes, commercial property taxes, and so on and so forth. It’s all passed through to individuals in the form of higher prices.