You’re not specifying a time frame for this statistic, so I’m going to answer based on the latest figures I’ve found, which are for 2007:
Total Social Security expenditures for 2007= apx $600 billion
Number of non-farm employees= apx 138 million
So if that $600 billion were spread equally (which of course it isn’t), each worker would pay about $4,300 over the year.
That picture will change rapidly over the coming years, of course, but that’s the current status.