I think parent's point was about free apps that are just access points to a physical world service like airlines, hotels, Uber, Yelp, OpenTable, etc. I do suspect iPhone users spend more per capita generally because they're probably a wealthier demographic than Android. But I also suspect that overall marketshare is more relevant to the companies developing the apps in this case. (It's also somewhat beside the point though because everyone in this position is going to have an iOS and an Android app at a minumum.)