Some choice stats in this article should be very sobering, and not just for e-retailers:

Amazon’s compound annual revenue growth rate from 2012 to 2015 was 20.5%.

49% of units sold worldwide on Amazon were by marketplace sellers in the second quarter, On which, for North American sales, it collects 15% commission on average.

It made a margin of 4.3% on its North American retail business last year, up from 2.5% in 2014.