The SS tax has been increased by 2% to 6.2%. If we assume the same rate of payout is still available in 2053 (my year of retirement at age 66) and my monthly income does not change, I would generate about $6,500.00 in a monthly paycheck from the government. (source: http://www.socialsecurity.gov/OACT/quickcalc/)
If, instead, that 6.2% was invested in the private sector (stock market), which has, historically, generated 10% investment return per year, then I would have accumulated $1.3M of retirement wealth. If I withdrew the investment income (10% annually) from that accumulated wealth, or almost $11,000/month.
Now, this doesn't have much of a direct tie-in with welfare, but it still jerks my chain that we're forced to participate in this system instead of being able to use that money towards something more.... profitable.
And the meme you quote is unfortunately, wrong. It's not wrong in comparison with quoted returns from social security, it is better than that.
Here's a guy that's done some simple work looking at after-inflation values of stocks and returns on them. He gets about 3%.
http://inflationdata.com/Inflation/Inflation_Adjusted_Stock_Price/NYSE_Inflation_adjusted_stock_price.asp