For a one-person startup where my time is more limited than my money? Absolutley. 30% is not unreasonable compared to what you would pay a distributor and a publisher for shrink-wrapped software. Even then you would have to manage several stakeholders instead of just one. Visibility is also something Apple gives you if you are fortunate. Once your app hits the Top 100 charts or gets featured sales just take off like a rocket. I've been featured 3 times and while getting an Apple feature is rare, your chances are significantly improved if you have something unique and polished.
