The wording could have been more clear: Instead of "what you'll pay" it should have said "what your organization will pay".

Everything else about the e-mail is clear that it's about the organization, though. I don't know why this person would think they're going to start getting bills "per committer" of the organization where they're not already the responsible party for billing. Like GitHub just decided that they're going to start billing this one person for every committer in the org, but only for this one feature?