Could you point me to any source where it is calculated? This seems especially suspicious, since high speed growth started only 200 years ago (in 18th century the average per capita growth in Europe was 0.1%), in 19th century the average growth was about 1%, and in 20th it reached 1.9%. This gives around 20-fold growth, which is hardly similar to 400-fold one.
I don't need it though. I have something in my hand right now that I could have sold for literally a million times as much only 60 years ago.
I can buy enough food for a year on a single weeks wages. Compare and contrast to an indentured peasant who worries if he's going to starve this year.
I can travel to the other side of the planet and come back. This is something I can purchase on about a week's wages. The cost to someone three hundred years ago to doing this was so much higher, and given that I can get there and back in less than 48 hours, it doesn't even begin to compare. My purchasing power (i.e. the things I can buy), compared to someone like me three hundred years ago, is so, so, so much more than a measly 400 times theirs.
For source, see http://piketty.pse.ens.fr/files/capital21c/en/pdf/T2.5.pdf