@andygreenawalt says he hasn't seen much on the economics of agility. "Open source breaks $ vs security battle. Investment impregnation kills agility."
Andy's comment arose from a discussion of agile security. I have written several pieces for the CBDI Forum on agile security - see the CBDI resource portal.
More generally, the economics of agility is critical to the business case for SOA, and a few of us have sometimes called it the SOA Sweet Spot (March 2007).
Looking around, I also found some work by Marc Rix called Bottom-Line SOA: The Economics of Agility (April 2007). See comments by Alastair Bathgate, Bill Barr and Gary Smith, with Marc's response.
And back in 2004, Stuart Robbins wrote something on the economics of agility for grid management (pdf).
But compared to the huge amount about the economics of scale (sharing, reuse), that's not much is it?