The use of "Pre paid vouchers user purchase of apps would increase developer margin".
Another option is "Pre paid account for user purchase of apps would increase developer margin".
By allowing vouchers as in "Nokia Music" store, purchases could be made without the 40% cut the SMS texts are costing via telecom services.
The user account by a one off payment via credit card.
The other alternative is to allow a two tier pricing structure for SMS price and credit card/account price.
The user account function allows for "quick" refunding of problems.
The users account should be connected to a verified email address on account creation. This would save all problems that plagued n-gage on its initial launch and lead to so much negative feedback across the Internet.
If n-gage had done this they would not have incurred such problems with phone lines being blocked with unhappy users wanting refunds.
This user account system would mean the purchase/refund systems could be tried BEFORE going live!.