Ask HN: Best Kickstarter Incentive for App Store?

Hi, my partner and I have several apps in progress for the Mac and iOS app stores, and we have decided to raise funds. Apple only provides 50 promo codes for each version of an app: http://arstechnica.com/apple/news/2008/12/app-store-lessons-creating-and-redeeming-promo-codes.ars So my question is, what if more than 50 people donate and we run out of promo codes? We have considered writing our own redemption system where we can enable custom codes from a central server, but this just seems way beyond the scope of what should be necessary. Another option is to update the version of the app, say every 2 weeks or a month, and give out a new round of promo codes, sorted by highest donor descending. A final option is to limit promo codes to the first 50 highest bidders and the rest of the donors would only get esteem for their trouble. If anyone has experience with this, advice would be much appreciated. Thanks!