How much buying power do you have for every dollar earned?

[mpatch]

Here's something else I wonder about which can be answered by those receiving Social Security benefits:

I know you have to pay income tax on Social Security benefits received, but does the .fed also charge Social Security/Medicare tax to those benefits? Wouldn't that be a bit like a snake eating its own tail?

You don't pay taxes on all of your SS, if you're under a certain amount it's tax free.
As to your initial question I would say for the average working person 40% of what they earn isn't taken in one way or another.