1) Producing goods involves waste and environmental destruction. This cost can be counted or not, depending on the power of the destroyer and the convenience of destruction. It still has an effect. How do we make sure that the waste an destruction can be processed by the Systems involved? If economics and waste breaks the boundaries of the earth system, then we are all under considerable pressure, if not dead. We are not yet able to treat the planet as if it was not a closed set of systems.
2) Wealth equals power in the market and in society. Power can be used to alter the structures of markets to prevent innovation and the distribution of goods to people who need them. This may not always have the effects intended, by those powerful. Hence a functional economics which is not just about protecting the wealthy, has to recognise politics and power inequalities and seek to subvert them.
3) Markets do not always work to maximise social benefits for everyone (through the “invisible hand” or otherwise, so it is probably false to claim that as a principle of economics. Perhaps we should more realistically start economics with looking at how markets do not achieve this, and are not intended to achieve this?
4) When dealing with climate change we should probably think about the general disorganisation, disruptions and costs that come from not doing anything. This is the base cost of action.
5) There is no reason to assume the least cost intervention will be the best, although it is, by definition, probably least costly to the powerful wealthy and therefore to be favoured.
6) We may need to identify those people who will resist any intervention, and why. This takes us out of economics.