"upgrades are not mandatory" -- lolz
I remember the last "not mandatory" upgrade. Let's see: I upgraded my Mac's OS, and TADA! Parallels announced it would no longer work, unless I upgraded. It did nothing. So perhaps you mean, "not mandatory...if you don't want it to do anything at all any longer."
Or when you say "not mandatory" you mean, "not mandatory...if you choose to leave your entire operating system locked in the past." Yes, then it would "not mandatory."
Of course you offer "special upgrade pricing"-- the same amount it cost me to buy this software, the same amount I paid for the last upgrade. That's not "special upgrade pricing"; that's "buy it again and again pricing, sucker." So put up a link and show me your special upgrade pricing. I see $49.95. You've gotten that twice from me already.
The joke is that you have a "subscription" for $49.95/year. Make no mistakes, everyone; even the purchase price is nothing more than a subscription because you will likely find Parallels needing 1 upgrade/year.
You may be "eager to clarify" but you're not trying hard enough. You only assumed/hoped that I tied so much of my business to Windows that your program became essential. It's not. The Mac App Store is not shrinking and the cloud does not have no fewer options than it did last year. I do not need to pay another $49.95 to keep my business running; you've only given me the kick in the pants I needed.