I bought Magix Edit Pro a few months ago for approx £30. I get messages now saying there is an updated version, but so can I upgrade to the newer version for free, or, would you have to pay for each upgrade?
See this article about the 365 update guarantee which started rolling out in 2016.
The biggest difference to some big software manufacturers is that if you do not continue the subscription the software stays at the version you have when the subscription expires and you can continue using the program.
Do note that if you have to re-install after the subscription expires, it does revert back to the original version you purchased, until you renew the subscription, when you will be updated to the latest version.
With some software manufacturers, if you stop the subscription you the software stops working.