I really can't imagine someone with CTO title doesn't have $15/month to pay for YouTube when you're a regular user. People with far fewer resources pay. This goes to content creators, if you're not even seeing ads, they don't get paid.
I'm pretty sure, that by this logic, if you combine all the "$15/month" things that someone should have money for, they'll eventually be left without any of that money. Every goddamn website wants $15 per month, and even after they get it, they still show you ads. Even youtube, if nothing else, there are the in-video ads ("this video is sponsored by,...") that an adblock skips.
This person likely can afford it and some others without any noticeable impact, I just don't find it appropriate in that circumstance. If you get $15 worth, and can afford it, pay $15, plain and simple.