To know whether that is unreasonable or not you'd have to compare it to the cost of providing you that service, taking into account that youtube is just a delivery mechanism and so is infrastructure, not content.
And what is or is not affordable is really dependent on where you live and that kind of money is a very large amount in some places. And especially in those places access to youtube for educational purposes can be quite important.
With all respect, do you have a source for that? I thought Alphabet was losing money hand over fist on YT before they started being so aggressive with the ads.
Let's for the moment assume that you are right, then they shouldn't have bought it in ... 2006, all of 17 years ago. And if they are short of money why are they pushing more and more junk on people? Let's start with switching off autoplay by default, limiting videos to 640x480, and offering creators to pay for the hosting so that their video can be shipped, just like I pay for the hosting of my web servers.
And what is or is not affordable is really dependent on where you live and that kind of money is a very large amount in some places. And especially in those places access to youtube for educational purposes can be quite important.