That's really stretching, are you suggesting that the £9.99 for your internet connection that you used for 8 minutes to download the iso and the £60 for the 500gb hdd in your computer is 'payment' for downloading commercial software (of which none of said proceeds go to anyone who wrote the software). I'm pretty sure even you're not convinced my that argument.
I think you might have missed my point. Relate it back to my last car/software analogy.
Of course it is quantifiable. It took X people Y hours to write the software, getting paid £z per hour. The bottom line is pretty much any software in those terms is a bargain.
Those are research and development costs, and they are seperate from (although related to and of influence upon) the cost of manufacturing a single unit of a commodity. It costs nothing (well, a relatively insignificant amount) to digitally "manufacture" a unit of software. If research and development costs equalled unit costs, then each car would retail for millions of dollars.