Apple must also make money in their own app store from ads, since every time I search for an app the first results are always ads for competing products. So ads

Apple must also make money in their own app store from ads, since every time I search for an app the first results are always ads for competing products. So ads and paid placement, unfortunately, would probably be the first monetization strategy for such a solution. Another option could be referral codes. If I find an app through the search site, the site could show a referral code that the app could accept, granting some benefit to the user. Of course this strategy means that the app makers must do work to participate.