With an average annual return of 1.77% in the last 10 years, July 2003 to July 2013, the cost of being in cash in VMMXX comes down to the inflation-adjusted return because inflation has averaged in excess of the nominal returns to cash: 2.43% annually over the period. That results in an average annual real return of -0.644% in cash. Ouch. By contrast, the real rate of return of the S&P500 has been +4.63% annually June 2003-June 2013, dividends fully reinvested. Going back 38 years to the inception date of VMMXX, 6-4-1975, the S&P500 has returned a real rate of 6.83% per annum. Cash has returned a nominal 5.58%, but with inflation averaging 3.95%, the real rate of return in cash has been just 1.568% per annum since 1975.
