I went through the pricing for Studio Manager 9 and made minor adjustments in your favor. Then I came up with this general set of discount rules for upgraders:
During December 2009 you get another 25% off.
So, for example, if you currently own Studio Manager 7, you get 45% off of the new price for Studio Manager 10. And, then you get 25% off of that number if you buy before January 1st!
A detailed price schedule is available at: Studio Manager Story Upgrades tab.