I think that many people here don't understand that the 15-30% fees that Apple charges to APP developers and platforms cause the products to cost more to end users.
Of course, just like at any retailer where they markup prices to make a profit.
Reality is... if the fees were mandated to come down. or dare I say it... the walled garden is opened by regulators so people who buy phones can install what they want without Apple surcharge or censorship... well iPhone and iPad owners would be able to get lots more things done and cheaper.
I doubt cheaper. Look at the Mac as an example. A quick check of several apps shows teh same price on the App Store and the web. Some may charge less, but since users are already paying the App Store price I suspect many would simply pocket the difference.
As for more things, perhaps, at the potential for more malware and piracy. Look at Android for that model. Many apps use IAP simply becasue piracy forces them to give away the app and use IAP to try to make money; having a pay once app only invites pirates to use it without paying.
As for alternative app stores, will they be able to provide the services Apple does and reach the customer base for less than 30% and stay in business? Cydia, arguably the most successful alternative to Apple, charged (drumroll) 30% for apps sold on its platform.
Strict EU laws may cause trouble for Apple.
I suspect in the end Apple will find a way to make up for any lost revenue to the detriment of developers who currently enjoy a rather good deal overall. Apple could, for example, charge per download or for every time a user searches for the app. They could give developers some free tier so smaller developers are unaffected while the EPICs and Spotifys of the world wind up paying more than they do today.
Apple could take the same sandboxing approach as they do with the Mac, and offer signing services, for a fee, to other app stores or developers to bypass it.
The old saying, be careful what you wish for because you may get it, might be appropriate here.