Marthambles,
Let's keep in mind that Botox is only injected by in a Doctors office, there is no self-injection.
These Doctors have a 15 year relationship with Allergan and if that relationship has been solid would they be willing to break it? Step Two is that Allergan has many more approved areas of use so Allergan easily could tie volume into its pricing model.
Can Revance sell? Of course, but it won't be as easy as anyone thinks.
Even today, with a self injecting, drug Momenta is only able to obtain 42% usage in the 20mg market.