It's good to do a cost-benefit analysis, but this is not the right comparison. It needs to be between the number of avoidable deaths caused by the lockdown and the number of avoidable deaths that would be caused by not having a lockdown, which is probably higher than 150,000. 1/ https://twitter.com/ClarkeMicah/status/1248634630657519616

In other words, a large part of the reason that the number of people expected to die of Covid is a lot less than 150,000 is ... the lockdown. (Why? Because around 60% of us would get it, of whom around 1% would die. And 0.6% of the country is about 400,000 people. 2/

And that death rate might be an underestimate because it would all happen over a few months, so hospitals would be able to treat only a small fraction of the people who needed treatment. 3/3

PS I'm not endorsing that 150,000 figure -- I have no idea where it comes from. But I do think it's important to try to do estimates of that kind.