It would appear, if the figures released as part of a settlement offer with Oracle are to be believed, that Android is not very profitable for the search giant Google. Additionally, the figures show that the iPhone is four times greater for revenue than Google's own Android. The figure suggests that Android handsets only make Google around $10.
Part of the reason the iPhone is so much more profitable is because of its use of Google Maps, YouTube, and other Google services. PC advertising makes up the majority of the massive $38bn total revenue from 2011. This equates to around $30 per PC, but not all PCs are connected to the internet, so this figure is a bit higher.
Google has never released any sort of numbers regarding the revenue from Android. It provides Android free to handset makers, and only profits off of adverts and App sales. Once again, these numbers are calculated off of court documents, so their accuracy is likely to vary depending on who calculates them.