It is expensive but even then Youtube has been profitable for many years now. It represents 10% of Google revenue. 5-10 ads is a cash grab imho.
How do you know this?
> It represents 10% of Google revenue.
Revenue != profit. Storing zettabytes of videos across the whole world, with the massive CDNs required to be able to serve that whole world isn't cheap. I can easily see YouTube being among the most costly things Google do.