In general I've never known anything with insurance in its title where what you get back is what you put in. What you may get back may scale with what you put in but it may be considerably more or less. Who gets more back: a millionaire who paid hundreds of thousands to FICA annually until he drops dead at 45 or a middle income earner who lives to 105?

Considering too that approximately 20% of FICA goes to fund Medicare and as far as I can tell Medicare receipts are based solely on need and eligibility rather than contributions even that tenuous earnings link is broken and it is simply a tax.