Here is the pdf of the 2007 Summary for Policymakers.
This summary, approved in detail at the 9th Session of Working Group III of the IPCC, Bangkok – Thailand, May 2007, represents the formally agreed statement of the IPCC concerning climate change mitigation.
I'm not in the mood to read it (35pages) right now, but skimming it I noticed there is a sizable portion dedicated to cost of mitigation and the effect on GDP.