We don't really know what the CGRP pricing is going to be yet. Also unclear if the third company to market (likely Lilly) with an equivalent drug might be forced to cut prices to gain traction.
I can't really believe the insurance companies will require step-therapy (fail Botox before using a CGRP) given the clear efficacy advantage here. For many patients Botox only really starts to work after the second or third administration anyhow - so that's six or nine months before decent efficacy. The CGRPs are more like a few days before efficacy. And the Botox procedure is not particularly pleasant for patients - indeed the majority of the patients at the place where I tried Botox have conscious sedation. (Remember some of these patients have allodynia).
Now the dynamics of the market may be that some of the docs giving Botox might not want to give up their lucrative gig and instead keep patients on the inferior drug - but those same docs are presumably going to prefer a three-month product to a six-month product.
So I'm personally skeptical there is going to be any significant first-line market for Botox-type drugs a few years out from here. And these trials are long and likely hard to enroll as well.