Do you really have to pay subscription for each device?

We recently bought a second Ring Device. I have already been paying a subscription for the first device. Do you honestly charge per device? If so this is very unfair.

Yes you do. It’s stated. Best plan is the $100 for a year. 3+ devices, central monitoring for use with an alarm and lifetime warranty on cams and such.
You don’t need it if you don’t want to see recordings. They will still work.