80% of the life time cost of software occurs after the sale is made

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.