The Linux Foundation has updated the 2001 study of David Wheeler which looks at the approximate cost of developing a typical Linux distribution using a methodology based on the total number of software lines of code (SLOC) present in the distribution.
The tool the Linux Foundation used, SLOCCount, calculated back then that the cost of developing Red Hat Linux 7.1 would be around USD 1.2 billion based on the 30 million physical source lines of code in the operating system.
Applying the same tool to the Fedora 9 Distribution shows that the price of building a Linux distribution has now gone up by 900 percent to reach USD 10.8 billion with the cost of building the Linux Kernel alone costing a staggering USD 1.4 billion.
The authors of the study took into consideration that it would take 59389 person-years of coding to churn out 204.5 million lines of codes and also used the average cost per coder of USD 75662, adding a further 140 percent overhead to cover benefits and other charges.
Overall, the Linux operating system represents a USD 25 billion ecosystem according to the same report.
The foundation also found out that more than 1000 developers from more than 100 companies - including quite a few Fortune 500 companies - contribute regularly to the Linux Kernel.
SLOCCount uses an industry standard called COnstructive COst MOdel (COCOMO) which is an "algorithmic Software Cost Estimation Model5" developed by Barry Boehm.
To put that in perspective, Windows Operating System probably cost the world several hundreds of billions of dollars in terms of sales and development time over two decades.
You can read the whole report compiled by Amanda McPherson, brian Proffitt and Ron Hale-Evans here.