Fastmail has three current tiers: Basic, Standard and Professional. Basic is $3/user/month, Standard is $5/user/month and Professional is $9/user/month. None of them are remotely close to $50/month for ordinary single users. You would need 10 users to get to $50/month for the Standard "non-lite tier" plan.

Perhaps the user has confused fastmail with another service or they might have some legacy plan which is more expensive than it needs to be. (I think I have a legacy plan...)