>>8
V6からもアップグレード価格で購入できるはずですよー。

このあたり参考
http://www.ashlar.com/shop/2d-3d-drafting-graphite.html

Electronic Download (E-Only. No Physical Materials)
Graphite v8 e-only: US $1,395.00
Upgrade from Graphite v7 e-only: US $495.00
Upgrade from Graphite v6 e-only: US $695.00

US $695.00　ってとこをクリックすれば、ストアーへ直接飛べます。

参考2
Upgrade Options
http://www.ashlar.com/sections/products/upgrade-options/upgrade-options.html