It was good to have it as a backup. I primarily use wireguard but now its a single point of failure.

Am I missing something or is the price higher after the 2nd year?

Yearly: $500 for first year, $400 thereafter
Quarterly: $150 every three months

$600 for 3rd year?

https://github.com/mumble-voip/mumble-docker

myself, I run a docker container of mumble in casaOS