Dewophile,
Basically what you are laying out is a price war and as long as Sanofi feels it's worth their time they will continue to negotiate with the large users.
This is somewhat surprising considering Sandoz's manufacturing limits at this point.
This product just might turn out to be a nice base income from which Momenta can grow and use to pay for its future products rather than the goldmine we were hoping for.
What's unusual in this product rollout is that because Sandoz was the only product approved, Sandoz priced its product high enough that Sanofi could easily attack it. It was Sandoz's original pricing that kept Sanofi in the game.
If more generics were approved originally, at an decent discount, Sanofi probably would have just folded its tent and closed shop.