ISIS doesn't need to increase their price. They have more drugs able to be marketed in the next few years, a pipeline that can continue that trend for many more, with a goal to produce 3 or more potential new drugs a year with a track record proving they can do so.
There is no way to know which will be successful, but the argument against ISIS is safety NOT effectiveness. If Kynamro proves to have a better then expected long term safe usage track record then that increases the the chances for all future developments.
Aegerion Pharmaceuticals needs to squeeze every dime they can. ISIS needs as many patients to use their drug as possible to setup the rest of their pipeline.