The S&P 500's top 30 stocks cost three times as much per dollar of free cash flow as the other 470, despite their stronger margins. Their net margins are 34% versus 17%, but they trade at 5.6x sales and a 1% free-cash-flow yield excluding stock compensation, against 2.3x and 3% for the rest. Half of an index-fund investment rides on those 30 stocks at the richest multiples in modern history. x.comÂ