The ϱ is the Greek letter "rho" which is the official symbol for density :) http://en.wikipedia.org/wiki/Rho_(letter) http://en.wikipedia.org/wiki/Rho_(letter)

The ϱ is the Greek letter "rho" which is the official symbol for density :) http://en.wikipedia.org/wiki/Rho_(letter) http://en.wikipedia.org/wiki/Rho_(letter) and http://en.wikipedia.org/wiki/Density http://en.wikipedia.org/wiki/Density Volume discounting is something we do have, just not on the site. Based on your feedback it seems it might be worth mentioning that on the pricing page. Thanks for the feedback.