There is a considerable difference between a well-managed exit that minimises the risks of an epidemic relapse, and a hazardous exit leading to another lockdown combined to a business downturn and a loss of confidence of economic actors.
Before trying to quantify the worst and best case scenarios, let us consider the health strategies implemented in France and in countries with a similar level of development. The report submitted to the British government on March 16, 2020, by a team from Imperial College London led by epidemiologist Neil Ferguson, attempted to compute the cost in terms of human lives (rather than the economic cost, which also translates into human lives lost, but in the future) in two polar cases: a strategy to contain the virus ("suppression") through drastic containment measures, and an alleviation strategy ("mitigation"). The report's findings reveal that demand for intensive care hospitalization would exceed eight times the country's capacity, even with an optimized mitigation strategy. This led Prime Minister Boris Johnson to make a sharp shift to a containment strategy through an extended lockdown.