Actually, there is a balance -- at least for Social Security. It's the "trust fund", which is a bunch of special treasury bonds. They really exist, on paper -- in a file cabinet in West Virginia. No, I'm not joking.
This balance (which is basically excess taxes from the past 30 years or so) is expected to be exhausted in about 2033. It wasn't so long ago that it was expected to be 2041. So, it is getting closer, and will probably continue to get closer. At that time, only enough Social Security taxes will be collected to pay 75% of expected benefits.
But, the "trust fund" is a balance for all of Social Security. Individual taxpayers don't have a balance. All you will get is the earnings that were taxed over your working career. That's what is used to compute your benefits: after all of them are adjusted to constant dollars, the highest 35 years are averaged.
Then, the benefit formula is applied. It's not linear, as this graph demonstrates:
However, this is all beside the point. In order to evaluate whether Social Security or Medicare beneficiaries receive more than they contribute, one must analyze it as if they really did contribute to their own account, and withdraw from their account. And in doing so, you must take the cost of money or return on investment into account. Since the trust fund is invested in the equivalent of long-term US treasury bonds, it's fair to use those rates for the rate of return.
It's hard to do it for Medicare, because you can't really predict medical expenses for an individual -- only as a large group. And it's not that easy to do it for Social Security, because as you can see from the graph: the relationship of contributions to benefits is non-linear. Lower income taxpayers get a great deal, and higher income taxpayers get screwed.
I did the calculations a while back. I'll try to dig them up and repost them.