With Android you don't have to go through their store. For example I bought one Humble Bundle [1] pack of Android games (which was quite successful) directly from their website. Then I got a link in my email for their downloads and I could install them directly.
> given how few people actually look anywhere else but the play store
I do not believe the truthfulness of this statement, considering how many services get popular outside any app store. Do you think people find out about Twitter or DropBox by browsing the app store?
> you are going to take a hit much larger than 30% if you are not in google play
It really depends on what channels of distribution you can tap into. Some apps are popular only because they get promoted on the play store. Other apps are popular by other means. And no, you don't necessarily need a middleman.
IMHO, Android is much better in every regard, because on Android the walled garden is optional for everybody.