If you are 100% Apple then you are probably right. But to me it is absolutely worth it just for 2 factor and being multi-platform.
I am 100% Apple at home and only use windows at work. I tend not to login to personal stuff on my work pc as I can just use my iPhone.
If it was cheaper I’d try it, but it’s probably 3x what I consider it’s worth.
If every good app I use wants £3 per month things would get expensive very quickly.