> Most sources I find online show a big discrepancy between expected app revenue from the iOS and Android worlds, so developing a for-profit app on Android first seems a little iffy to me.
This is somewhat self-fulfilling. There are very few developers of paid apps that put equal time and effort into developing both on iOS and Android and release paid apps on both platforms (instead of freemium on one)[0].
Of those that do, many simply make one or the other (usually the Android one) either a simple web view shim, or a naive port of the app design from the opposite platform, which usually looks as bad as you'd expect it would.
So in the end, it's not surprising that some companies report dramatically better sales on iOS than on Android. It's not very straightforward to compare them, because they're essentially shipping two different products, one on each platform.
[0] I'm only talking about paid apps for which app revenue (including in-app purchases) is the primary business model. In other words, Facebook and Twitter would not count here, since they make their money off of advertising.