* Apple processes payments and wires me money
* Apple processes over 1GB of downloads per day for me (and growing)
* Apple makes my software discoverable to their hundreds of millions of already-entered-my-credit-card users
Also, for expensive apps, 30% might seem steep. But I challenge you to find a payment provider who will let you sell something for .99 and wants much less than 30%, as a fee or percentage. Plus, you can avoid the 30% if you want by having a free app with in-app purchases that you process via some other mechanism.