Energy is cheap in that most sources have low marginal cost and high CapEx. Building energy capacity is largely an exercise of capital formation and deployment. These capital expenditures have fixed capacity, and lifetimes. If the capital formation and deployment process breaks down for some reason, then there will be an energy crises as demand outstrips supply. The cost of energy in such a market is not the marginal cost of an extra kWh but instead the marginal ability for energy purchasers ability to pay which for many use cases is orders of magnitude higher than the former number.