No sooner had AdMob made the announcement than the headline writers went in to overdrive.

For every $1 spent on Android apps each month, AdMob claimed, the Apple app store generates $40.

The message was simple. Software developers wanting to make money should disregard the Google offering.

Even though Android users make use of their apps for 88 minutes each day, 4 minutes more than iPhone users, it seems few bother to pay for them.

According to AdMob, half of iPhone users are happy to part with money for at least one app each month. By comparison, a mere one in five Android owners will currently countenance using their credit cards for the same purpose.

And whereas the minority of Android owners buying apps average only one paid-for app each month, iPhone users average 2.6 as well as paying higher prices.

Then there's the fact Android users download an average of 8.1 free apps each month, iPhone users 7.6.

As some commentators have noted, perhaps Android owners subscribe to the Google catechism that software should be free.

More pertinently, as AdMob calculates, it means that each month a combined total of $198 million is being spent on apps for the iPhone and the iPod touch, compared to $5 million on their Android counterparts.

Yet even that may overestimate the real value of the Android marketplace.

For example Matt Hall of app developer Larva Labs notes: “As sad as that (the AdMob) comparison may be, from our experience the total is probably much lower.”

Despite having two games in the Android Top 20 as well as marketing two other apps, Larva Labs total Android sales in August averaged a mere $62.39 per day.

As Hall says, it’s going to be “very difficult to buy the summer home at this rate.”

He also quotes the example of Trism, a game from another developer that in its first two months on the iPhone generated more than $250,000 in sales. By his estimate that the same app on Android has made “$1,046 total earnings, max.”

Were those numbers to be typical across the board, the sales ratio between the two platforms would be closer to 250 to one than AdMob’s suggestion of 40 to one.

Part of the problem, Hall argues, is caused by the mechanics of the Android Market itself, such as no screenshots, a maximum of 325 characters with which to describe any app, and forcing purchasers to use Google checkout.

As if in response a report on Cnet suggests a new look with an updated user interface is on its way for the Android Market. And Hall still remains “excited about Android in the medium to long term,” although “whether it’ll be possible to target it profitably as a small developer I’m not sure.”

In explanation, compared to a user base of 50 million iPhones and iPod Touches, there are at present just 3 million Android handsets. But with the imminent launch of a number of new Android phones, that gap could well narrow appreciably.

Should it do so, then Android app developers can only benefit. Provided, of course, that the next generation of Android owners acknowledge that not all software should be free.

And that is the crucial known unknown. As of now, the evidence is not encouraging.