Everybody who studies the cost of climate change finds that not acting is much more costly than acting, by a large margin. One recent example is from the Canadian Institute for Climate Choices, which found that the impacts of climate change amount to a 5% drag on GDP.
The same analysts looked at the expense of Ontario's cap-and-trade program back in the day, and they saw that it would cause a bit of a drag on the economy, but only by 1.5%. This is just a percentage of growth, slowing down the growth of the economy by a bit. The cost of putting a cap-and-trade system is one-third of the cost of ignoring climate change. That is one example.