That said, there should certainly be no restrictions to creating your own versions of things you own in other media.
I totally agree that an audio book has an entirely different production path and it's own entirely different staff and company that needs to make it's own costs back. But that argument is becoming less and less relevant for physical vs digital books.
Many non-traditional/smaller publishers and printers, such as No Starch Press, offer free copies of the ebook version when you purchase the physical copy and offer the digital copy at a reduce price compared to print.
Audiobooks I'd say are new works. If you buy it on a medium you should be allowed to rip it and vice-versa, however (currently not allowed in UK).
Sure, but it's worth something to you.
I just downloaded a productivity app. The free version is great, so I don't think I need to upgrade, but I noticed that the paid version includes a Pomodoro timer. Would it cost anything for the company to turn on that feature for me? No, of course not. It's clearly just an attempted to make more money. But an attempt to make more money is exactly what they have a right to do. That's why they're in the business.
The only inhibition to me making or acquiring a copy of a book in my preferred format is copyright law, I already have a copy on paper; I can download or make a copy easily. That should be allowed as I have paid for a licence to the work (and I think is allowed under Fair Use in USA). As the copyright holder already has a digital copy the restriction of it is silly -- for the demos, who supposedly give the rights in copyright, the benefit lies in making that copy of the work available rather than forcing the extra work of having someone scan it and upload it and make it available. This later route also enables copyright infringement far more readily than the former does.