According to Bill Hare, one of the lead authors of the report, the cost is manageable:
HARE: Well, over the period to 2030 it’s going to cost about, maximum, I would say about 0.1 percent loss of annual GDP growth globally. I’m not sure that would really be detected in terms of the year-to-year variations in global growth.
“It has been shown for the first time that stopping climate pollution in a very ambitious way does not cost a fortune,” said Stephan Singer of the World Wildlife Fund.
0.1 % of GDP growth less per year is not a "fortune" since it dwarfs the wealth of, say, Bill Gates. I'd say Mr Singer should be more careful about his choice of words.
He's getting damn close to "a trillion here a trillion there and soon your talking real money."
I'm sure it's worth the cost, but it's a lot of money and there is no point pretending otherwise.
(I assume Hare means 0.1 percentage points a year not 0.1 percent of gdp growth of 3-5% in which case it would take a while to dwarf Gates's fortune).