Google’s crazy expensive $12.5 billion purchase of Motorola has been finalized earlier this year, but the Search giant is yet to really take advantage of it.

A Google exec revealed a few weeks ago that the purchase was mostly about the patents rather than building Motorola Nexus devices – although recent reports do suggest that Google and Motorola are working on both a new tablet and smartphone – but those patents failed to help Google deliver any decisive blows to its main rivals in courts, Apple and Microsoft.

But now Forbes says that the $12.5 billion purchase may not be as expensive as it sounds, suggesting that the deal will only cost Google $1.5 billion on the long run. But is that really so?

The publication argues that Google got some of its cash back by selling the Motorola set-top box to Arris, but that the real win for the company is Motorola’s unprofitable business – yes, no joke. Apparently Motorola’s “accumulated tax losses” can be used by Google in its tax reports:

“The tax benefits of the deal make what was a good deal into a great deal,” said Robert Willens, a New York accounting and tax expert. He estimated that through the acquisition, Google can expect to reap $700m a year in tax deductions from future profits each year through 2019. Google also will be able to immediately reduce its taxes by $1bn due to Motorola Mobility’s US net operating loss, and by a further $700m due to its foreign operating loss, he said.

Do we want Motorola to keep bleeding money through to 2019 so that Google can write the losses off its tax bill? We’d rather have Google turn Motorola around to make it a profitable subsidiary and a worthy rival to other Android OEMs. We’re no tax experts, but wouldn’t that be the proper way to recover the $12.5 billion investment?

Meanwhile, it’s late 2012, and the fact remains that Google paid a lot of money for a business that’s yet to be lucrative for the company. Anyone looking forward to a Motorola Nexus device?