I don't understand your point, you can't start a Telegram call if you aren't a Telegram user as well.

Anyone can become a FaceTime-calling Apple user for a mere $199. https://www.apple.com/ipod-touch/

Anyone can become a Telegram (or Signal) user. For $0, infinitely less than $199.

I wonder how could you make a Telegram video call with no device. Or android devices are free?

Free, no. Less expensive and more widely available than iOS devices, yes. Telegram also works on Linux, Windows and MacOS. There is a web version as well which works anywhere there is a reasonably recent browser available. The web version does not yet support calls as far as I know, this will most likely be added in the near future given that it is a rather trivial addition with plenty of free-software implementations available.

a telegram account is free, a facetime account requires an apple device.

an iCloud account is free, a Telegram account requires a device. ¯\_(ツ)_/¯

He means that you need Apple hardware to start a Facetime call.

That's my point too, you need hardware anyway for a Telegram call. Whatever device you use has an inherent cost.