Last year, median family income was $53,891. [This means half of the households were lower, half higher.] One thousand times $53,891 is $53,891,000. [I take it this is not controversial, although these days, you never know which parts of math and science Republicans will object to.]
My proposal: No young person should inherit more than a millennium of median household income [in 2015 dollars. Who knows what the dollar will be worth in 3015?] So, when a billionaire or multi-millionaire dies, he or she can leave $53,891,000 to each child, and all the rest will be taxed by the state. The proceeds can be used to reduce the FICA tax.