When I asked, some time ago, I was told the commercial model for the software was based on the customer business needs. They need and can afford to pay the prices asked.
We are in a niche area of astronomy where - for whatever reason have developed software like PS to dominate our thoughts for image processing. We probably represent less than 0.00001% of the global user base.
I started with PaintShopPro many many, years ago - when it WAS a paint program but over the years (and being purchased by Corel) it has significantly changed to meet the needs of professional photographs who need the bells and whistles to compete. The screen layout and capabilities now mirror PS but (as yet) they have not changed from a one off (reasonable) payment.
If I have a need to tweak images I now use PSP2022 (comes with added 64 and 32 bit options to allow some astro plug-ins to work)
See:
https://au.pcmag.com/photo-editing/4...-paintshop-pro
All I'm saying is there are many other great image processing software packages which may be more cost effective to the amateur astronomer.