Create new SKU = sidestep providing updates to application in perpetuity.
To expect updates in perpetuity, or even heavily-discounted upgrade deals, is not reasonable or sustainable when the original product cost $30 or less (I think I paid about £10 for Pixelmator when it was on special).
What is easy to forget is how much the App Store and its like has driven down software prices. We all know how much Adobe subscriptions cost and, pre-app-store, even "prosumer" grade apps like Pixelmator might easily sell for $50-$150 for a single-install license (whereas App Store licenses are valid for all your personal Macs). Even then, you'd typically only get free upgrades up to the next major version, and then maybe a discount on the major upgrade.
...where it is different is if you buy something that is known to be a "work in progress" and basic, no-brainer features that were supposedly on the roadmap never actually appear, while all the effort goes into flashy stuff, iPad versions etc.
Although I got Pixelmator when it was on offer I've mainly stuck with Photoshop Elements because - for website work - there's a lot of boring import/render PDF/crop/resample/export-in-specific format and bit depth, and even the cut-down PS Elements 11 I'm using is far, far better at that than Pixelmator or Affinity Photo (at least, the last time I tried).
I bought Affinity Designer shortly after it came out - because it seemed that, finally, there was an alternative to running Xara in a Windows VM (or putting up with the clunkiness & price of Illustrator) - but, several years later it is still as much use to me as a chocolate teapot. Why? Because although I'd love to spend my time producing cool photo-realistic artwork (talent upgrade may be needed) what I
actually need to do much of the time is diagrams, charts, graphs etc. and Affinity comes to a shuddering halt every time I need a dimension line or anything else featuring an arrowhead. It's a basic feature of every grown-up vector illustration package and has been on the Affinity "to-do" list since for ever, and if you look on the Affinity forum you'll see appeals for several other bits of basic vector graphics functionality that are apparently less important than touch bar support. Pity, because overall it is great - but I end up not using it because, sooner or later, I'll need an arrowhead, or a warp, or a blend and will have to go back to Xara.
