In the comment section of their website, there are comments point out that there are externalities associated with using the electricity. So some people question the logic of simply comparing the USD cost.<p>However, it's the beauty of comparing the USD cost. All resources are limited and all products have externalities. Comparing the USD cost makes the cost of things comparable. It may not be perfectly accurate, but it is the only doable way to compare all sorts of costs of all sorts of spending.<p>There might be a fair point that the externality of electricity has not been sufficiently factored into the cost. It might be reasonable to add more tax on electricity. I think it's totally a reasonable argument. However, if you do add more tax on electricity, don't forget everything will get more expensive, not just Bitcoin mining.