Honestly, I'm not sure - hence them not being listed - but I think I'm going to go with 30%. And then for people making >$x a month dropping that in tiers. Thoughts?
You'd have to write up some very specific usage scenarios that make that cut viable.
Apple's cut makes sense so far that you get some tangible advantages in terms of such things as exposure. You'll have to explain people what they get for the 30% cut.
Right now, I'm unconvinced that you get 30%'s worth. But, on another note, it's probably always better to start at a high price and dial it down than to launch a product and increase the prices over time. People will be crying bait and switch - justifiably.
PayPal's micropayments pricing is 5 cents plus 5% per transaction so this combination can be a big money saver.
We created a service for a niche market that was mostly using eJunkie at the time (lowest cost, word of mouth travels fast among groups of sellers) and we had to compete with them on price and features.
What if you went with max (5%, 0.01/MB)? 30% of 0 is still 0, after all.
30% is definitely high. I understand 30% has become a buzzword these days, but in reality it cuts a lot into merchants' margins. You may want to research on current digital goods market sites such as e-junkie, payloadz etc. Most seem to have a combination of monthly pricing and a "low" per transaction fee. Monthly fee certainly going to be a barrier for casual merchants.