I am reliably informed that a CEO of one of the competitors in the same space (RA biologics) claimed he could set the price of his rival drug at zero and it still wouldn't get on some formularies.
I can't say I fully understand the dynamics, but it has something to do with rebates and Humira having a broader label. So I could speculate that the rebates depend on hitting a minimum sales level and if you removed RA sales from Humira there would be a huge hit on the other indications.