It's an "arbitrary" number in the sense that it is the revers of the previous industry standard in the mobile space which was 70/30 in favor of the Carrier. Often times developers would get less than %30 of the revenue for their products. And they had many more hoops to jump thru to get to the market, could only even get a meeting to try and get on mobile devices if they were already a large company, and had to work with terrible SDKs, etc.

Apple democratized and revolutionized that entire industry, providing a level playing field where I can compete with Omni, and we both have the same hoops to jump thru and get the same deal. We both get a much better deal than before.

The $99 fee covers the cost of administering the developer program. This program is hugely popular, and is already overrun with people who just want to get access to early versions of iOS before they are released publicly. Even with the $99 fee. It's a very low fee so that anyone serious can afford it, but high enough to keep out the problematic people who would abuse the service and overwhelm Apple's developer support resources.

Seriously, I find it kinda curious that you're complaining about $99 as if it's some big barrier.

The idea that an "Apple centric skill-set is not transferrable to other platforms" is pretty darn silly. I mean, sure, if you learn to program using Cocoa you will be frustrated and annoyed at how terrible certain other platforms are to develop for.

But these days only HR people seem to think that programmers can only learn one langage and that experienced in one language is not useful in other languages or using other frameworks. Are you an HR person? Because that perspective is not one I would expect from any software developer.