I’m not necessarily disagreeing with you, but that estimate could have been wrong by a factor of 10 easily. The idea of an “average video” being 50MB, for example, is questionable: at typical bitrates of 1080p videos this would amount to about a minute-long video. I don’t think that’s an average video at all. It also doesn’t account for many things, for example the cost of replicating new videos to the CDN.
I also don’t find the idea of YouTube not being profitable ridiculous or hilarious. YouTube definitely wasn’t profitable before monetisation, and Google used to run it for prestige and data collection purposes at a financial loss. They clearly have been trying to make it more profitable, but whether or not they have crossed the break-even point in the past or are still hoping to cross it in the future is not as clear to me as it is to you.