Well, I assumed when they said "cash", they meant "yen", and the Japanese economy isn't so stable.
And are you sure the American dollar has remained stable? Sports cars in the 50's and 60's cost something like $6,000 and that was expensive. Now they're $80,000 or more. I read somewhere the average anual income before World War I was roughly $1,200, and now it's much higher, although proportionally they're the same. That would seem to indicate the dollar's been going down steadily for most of the century.