The developer version of Debian GNU/Linux contains 17,141 packages of software, or 419,776,604 lines of code. With that figure, James Bromberger estimates that Debian would cost about $19.1 billion to produce. Bromberger also looks at the cost of individual projects like PHP, Apache and MySQL. Even at more than $19 billion, the figure is likely far short of what it would actually cost to produce.
Bromberger is following the same methodology that was used back in 2001 to estimate the cost of developing Debian 2.2 ("potato"). Debian 2.2 was estimated at $1.9 billion, which demonstrates just how much Debian and the upstream software ecosystem has grown in 11 years. The estimate uses the SLOCCount tools from David A. Wheeler, which "automatically estimate the effort, time, and money it would take to develop the software." It uses the Constructive Cost Model (COCOMO) to estimate costs. This assumes that the average developer wage is about $72,533.