Revenue. From earnings release for 2024 Q3[1]: "YouTube's total ads and subscription revenues surpassed $50 billion over the past four quarters". 2024 Q4 says: "Together, Cloud and YouTube exited 2024 at an annual revenue run rate of $110 billion."

[1] https://abc.xyz/investor/

Last I checked, Alphabet still doesn't break down profit/operating costs for YouTube.