Apple
I think they forget to mention that Apple has 95% of the mobile app market. The rest of the planet will probably makes 0$.
Smartphone owners will together spend a staggering $6.2bn on applications this year, market watcher Gartner has forecast. The company calculates that, in 2009, we spent $4.24bn, and with analysts unanimously anticipating yet more iPhones, BlackBerries, Palms and Android handsets to be purchased in 2010, Gartners' predicted …
I quite agree regarding the money making opportunity, but from the point of view of the platform would suggest this doesn't do Apple any good at all.
Case in point: I saw one of those iPhone ads the other day pointing at - among other apps - a VNC client for a whopping £14.99. Now, it isn't a secret that Apple users are overcharged for their products but a very effective VNC client on my Android (or my previous Windows Mobile) cost me zero, zilch, nothing. Whatever additional benefits the iPhone version MAY provide, I doubt they're worth that much.
The public are taking note, and the high cost of iPhone apps is beginning to grate. Yes, there are thousands of fewer (fart) apps on Android, yes market forces may eventually synchronise the two, but it isn't going to take a lot for Apple owners to be branded with a more-money-than-sense stigma that has done for other designer brands.
Can't speak about all platforms, but I can say that where the same app is available for iPhone as it was for my previous phone (SE p910 - Symbian) the iPhone versions were substantially cheaper than the p910 version used to cost. Interestingly, in the case of IM+ the cost of the Symbian version has now dropped to the same as the iPhone, while QuickOffice is still cheaper than the Symbian or Palm versions.
If anything, from where I'm sitting, the prices for iPhone apps have been driving down the costs for other platforms.
... of extrapolating from a single point
It does sound as if Gartner (quick: who said "The thing I love about science is that you get so much speculation from so little data"?) have taken one year's sales figures and presumed that every subsequent year will follow the same pattern. Conveniently forgetting that all the early adopters are the monied fanbois who are willing to buy anything if it's shiny enough.and has the right logo associations.
When smartphones start to be used by "real people" I think they'll quickly find that the proportion of users who are willing to pay for applications is a small percentage of what the first generation did. Further, I'd guess they are likely to have far fewer applications (paid or free) on their phones, too.
Now we all know this isn't just a survey, it's a GARTNER survey, but I still wouldn't bet my future income on it's accuracy or validity.