Paying $ 250 for such a system is ok.
Paying $ 250 EVERY year if you don’t make money with it is NOT.
Funny thing though - Unity plugin is $150 WITHOUT a subscription.
If is true that’s one pretty bad offer.
Being forced to pay regularly to be able to use piece will stop me from buying .
And maybe some other guys too.
Think you should reconsider your license/subscription model…