Cast gold, the most common "trade form," has a density of 19.3 gm/cc

40 feet = 480 inches = 1219.2 cm

A cube 40 feet on each side contains 1,812,278,181.9 cm³

One cm³ of cast Au has a mass of 19.3 gm

The 40 foot cube of gold has a mass of 34,976,968,910.7 gm

1 troy ounce is 31.1035 grams

The 40 foot cube of gold contains 1,124,534,824.3992 troy ounces

At the nominal value of $880 (US)/troy ounce given in the first post, the value of "all the gold there is" according to the estimate imputed to Asimov would be:

$989,695,365,471.30 (US)

But what does that have to do with the worth of everything else?

John