Fair points on everything, however, I have never had a buggy experience with PDF Expert, although thinking about it, I have had the odd crash, they do provide regular updates so my experience has been very good. I think you're right that Adobe has a monopoly, so it's all about how much people are willing to pay.I used to think that way about PDF Expert, until I actually tried using it as a daily replacement for Acrobat in my work. Many of the features are indeed there, but are often buggy, incomplete or do not work as well as Acrobat. The same goes for most other PDF software developers. Many of the bilingual PDFs I have to handle on a daily basis fail to display correctly in PDF Expert, and the app wasn't as stable as I'd hoped it would be. I may go back and revisit that app someday to see how it's evolved, but I wasn't particularly impressed by my findings last year.
The fact is, Adobe has always had the cornerstone on PDFs, for better or for worse. (Maybe "monopoly" would be a more realistic term for this...) Adobe opened up their patent on PDFs in 2008, but I really don't feel that the market has made a reader/editor that surpasses Acrobat in terms of stability and functionality. After all, Adobe developed the PDF format, nearly three decades ago.
No different from Microsoft imo, but Microsoft only charges $99 (family price) per year for its entire suite which includes up to 6TB storage whereas Adobe Acrobat is $240 for the single app.
Adobe is basically a rip-off compared to other excellent companies and it's the reason people are walking away in droves, to pay for something that suits their workflow.