I pay a very small fee for debrid and VPN servers that offer exactly the same server capacity with enormous bandwidth and virtually no downtime.
Did you just compare your small private server with YouTube’s infrastructure? Jesus Christ.
Google had already been paying about 2 million a month for bandwidth in 2015 or so.
I work for a larger company as a software developer, even with a billion in gross sales, there is absolutely no chance to provide even a tenth of YouTube’s service. Especially for free (without paywalls). The company would go bust in two years.