Twitter's mMAUs (monthly Monetizable Active Users) stands at 450 million. If they pay $8 per month, that gives Elon $3.6B per month. It will take 13 months to make $44B - the purchase price QED. Elon Musk is a genius.
According to my observations, users are in no hurry to buy blue marks on their profile,so your calculations are incorrect.Most of the profits will be from advertising,so it has always been and will be.And even if they introduce a cryptocurrency (which is still unlikely),he will not receive a tangible profit.