The fair market price of an entire app pentest of that legal dashboard application, one which would almost certainly find that bug† if run by a competent, reputable firm, along with many other bugs, run by consultants with bios and concluded with a deliverable that Facebook can file away, is probably somewhere between $20,000 and $35,000, so the idea that the fair market value of a single finding of that engagement is $75,000 is pretty hard to take seriously.
From my perspective, people weird ideas (in both directions!) about how much this stuff costs.
† It's a little tricky to say because the blog post is cagey about what the vulnerability actually is, but I'm thinking about all of the password-reset-flow bugs I've ever seen that fit the rest of the pattern of the post and I'm pretty sure this is low-hanging fruit for a serious app pentest.