In the long term, I think Amazon, PayPal, and mobile carrier payment mechanisms will work well for selling direct to customers. Amazon and PayPal charge less than 10% per transaction. I think in a couple of years, mobile carriers will be charging ~10% (like the Japanese carriers do). Once this happens 70%/30% will seem ridiculous and will only be tolerated for platforms that give developers no alternative, like the iPhone.
In regards to the payment, i just meant that if oneforty offers the payment (presumably via Amazon or Paypal) the developer has less to worry about. I understand that this will only work if rates are not much higher than through those payment providers directly.