You can still make fortunes and/or have an interesting career with other platforms and technologies too.
About 77 million of the "big two" (60 million Android, 17 million iPhone) smartphones shipped in Q3 2011. Apple has a huge install base, but it's not Apple's game anymore - Android has more than 3x Apple's marketshare, and is on a meteoric rise in contrast to iOS's slow marketshare decline. More and more customers are being introduced to mobile devices, and we're still in the early stages of the mobile landgrab. There's a lot to be won, but it's disingenuous to focus on Apple as the nexus of that growth.
His summary: Android=$4428.08, iOS=$5914 (over the same time period)
So it is true that Android users spent less, but not by a huge amount.
iOS = $5914, Android and iOS = $10342.08
Between the question of statistical significance and the vagaries of mobile app promotion and discovery, it's hard to say that one clearly pays better. However, both usually pays more if one is paying well, so it would often pay to support both as soon as it is practical to do so.
Because this (and several other comments on this submission) appear to attack Gruber for not talking about Android, and I think that is an extremely unfair criticisim given that he was speaking to iOS and Mac developers at an event about iOS and Mac development.
More generally, I have a morbid interest in HN's tendency to flip it's collective shit whenever Gruber's name is mentioned, and have honestly lost faith in my ability to tell when that sort of criticism is intentional or not. So when presented with something that sounds a little dubious, I'd like a clarification. There have been times in this site's past where that was not offensive to anybody.
I hope that answers your question.
You know that's not what he said.
I don't understand why you take issue with my asking a question but then feel permitted to tell me what I know, but I don't care, either, so there's that.
Did I miss something?