Aren't trial version work exactly that way? Use ads at trial version and remove the ads once users bought the app. This is the common practice when IAP does not available back then.
The advantage of trial-paid method is that users know in advance about the app price prior downloading the app. The disadvantage of it is that it only has one set of price.
On the other hand, the free-IAP method has disadvantage of user never know whether the app actually free or are there any payments needed. But it has advantage at it can deliver more than one set of goods. Pay 0.99 for feature A, and then another 0.99 for feature B, etc. This can be handy for a big apps which usually high priced since all features are combined. But on the other side, users might not need all features. By breaking into smaller features, it's a win-win for both devs and users.
03-16-2015 12:00 PM