I'm sure some would have already realized but thought I'd post for anyone who had not noticed. When buying gems from the AH, check for the 'Perfect' Version of the gem you want. The 'Perfect' version is when a green quality gem is cut (RNG) into a blue quality gem.
Generally, the 'Perfect' Gems are much cheaper. For example currently on Tuyralyon EU;
Brilliant Primordial Ruby (+160 Int) Best BO 80G
Perfect Brilliant Pandarian Garnet (+160 Int) Best BO 32G
Not same with all gems, but more noticeable on the raw stat gems