Right now it's probably best to go to AppMobi for support, we haven't tried it ourselves so they're the best people to help you there.
I think there tends to be a small developer fee for two reasons:
1) keep out 'script kiddies' who just want to mess around - they won't bother if it costs them money, and
2) keep out viruses and malware, since if anyone submits any, they've got the author's payment details which is a great place to track someone down!
TBH if you're serious about app development $99 isn't a big hurdle, it's more there to keep the wrong people out IMO.