X, which is what Musk renamed Twitter after his debt-laden $44 billion deal for the social network, generated about $1.8 billion in ad revenue in 2025, per SpaceX’s IPO filing — less than half of the $4.5 billion in ad sales Twitter reported in 2021. As of the end of March, X had about 550 million monthly active users; of those, only 4.4 million were paying subscribers.