There's a difference between financial costs and economic costs. Financial cost is essentially actual outlays of money that people.... Economic costs can factor in externalities and the costs of doing nothing and so on. I'm talking about collective action problems. It's not just what Canada does. If Canada and other countries step up, do their part and avert catastrophic climate change, then the economic costs would be positive to doing that, in the sense that a much hotter planet will have all sorts of other negative economic costs associated with it, which the insurance companies are dealing with already.
There is a financial cost to most measures, but the question of an economic cost brings in more factors such as externalities. The whole reason that all of the countries of the United Nations are trying to work on this is that they feel that the economic, health and environmental costs of not combatting climate change are worse than combatting climate change.