If I were a manufacturer of software of any clout I d tell apple to go eff themselves and not sell from the mac app store. 30% fixed cut? Are they joking? For what? For storing a file on their server? For the review space? There might be some rationale for a cut in ios devices but what's the rationale of a 30% cut on the mac? If apple want to offer a service to their users where they can purchase with relative safety and ease on the mac, as well as see everything together they should forego the 30%, it's simply ludicrously high, and it benefits neither the dev nor the end user who has to pay more for apple to cover the cut, but only big fat filthy rich apple.
How about for the millions of users to which you can directly sell with only doing as you suggest - providing a file to Apple to sell.
It's actually a no brainer for any app developer to not sell through the store.
Seriously, so Adobe has different avenues to sell directly, through the channel (Amazon), boxed stores etc.. so why not add what's only the largest app store around.
Oh, and that store sells directly to the end user with 2 clicks of a button and a few password key punches.