Not necessarily ‘billionaires’ proper, but large corporations and consolidated mergers have: Rockefeller of Standard Oil reduced the price of refined kerosene from 26 cents to 8 between 1870-85; average costs fell from 3 to 0,452 cents in that same timespan; [1] U.S. Steel (run by the Edgar Thompson company, in essence a collection of speculators) reduced wire nail prices from $51 to $36 from 1901-11; in the same time, steel bar prices fell from $33 to $25, steel beams $36 to $27, billets from $27 to $24, and this was while wages for steel workers had risen 25%, as did coke and limestone prices 10% [2][3][4];
Name one time a billionaire has lowered your bills