Here’s an example paper estimating the number of years of life expectancy lost is ~10 years.
Note that in the UK for example the average age of COVID deaths is around 80 with many of those from care homes where their life expectancy is particularly low. This statistic makes the figure of ~10 years of life expectancy lost fairly plausible.
If lockdown reduces the quality of life of the population by 10% (conservative estimate IMHO), then each month of lockdown for a country with a population of 60M corresponds to 60M * 0.1 = 6M months = 500k QALYs lost. The average number of life expectancy years lost for a death by COVID is estimated to be ~10 years so 50k COVID deaths ~= 500k QALYs lost. This means that in a population of 60M you need to expect to be saving 50k COVID deaths every single month of lockdown just to break even and this is using a conservative estimate of the reduction in quality of life and ignores all other factors such as the damage to the economy, impact on third world countries etc. Currently the worst hit country in the world is Peru with a death rate of ~0.1% of the population which would correspond to 60k deaths in a population of 60M. 60k deaths corresponds to a little over a month of lockdown reduced QALYs in this analysis.