Forbes: Thanks to a buoyant stock market, the richest people in the U.S. just keep getting richer. That has made it harder than ever to join the ranks of the 400 wealthiest Americans. The price of entry to The Forbes 400 this year is $1.55 billion, the highest it’s been since Forbes started tracking American wealth in 1982. Last year it took $1.3 billion to score a spot. Because the bar is so high, 113 U.S. billionaires didn’t make the cut.