Pricing has not been set and it's entirely possible that 3D VoD titles will be free at first in order to build momentum and to ensure viewer lock-in of the all important child demographic.
They are constantly trying to churn out titles as quickly as possible, with DLC added (or restored to the game depending on your take on things) in an attempt to rake in more money.
It's possible that this could mean that they're simply going to rerelease Xbox 360 versions of current Xbox titles, sort of like how everyone bought Led Zeppelin IV all over again when it came out on CD.