I was told last week that:
60%-80% of the life time cost of software occurs after the sale is made, and
10% of that is down to poor documentation.
I’ve been trying to track down the original source of this information and it appears to come from Dr Roger Pressman and some Dept. of Defense studies. I’ll be including the sources I’ve found in our next newsletter, due out later this week.
I came across a similar statement, which suggests that between 60% and 85% of the system cost occurs in “maintenance, integration, support, and training.”
The statement is presented within the context of a debate about the benefits of open-source software for less-developed countries, and is not itself referenced.
http://firstmonday.org/issues/issue8_12/ghosh/#g2
The sources I found were
http://www.stsc.hill.af.mil/resources/tech_docs/gsam3/chap12.pdf and http://www.rspa.com/