It’s so simple. (1) Your economy will be hit whether or not you lockdown. People are gonna reduce their activity due to the threat of the disease.

The lockdown affects behavior at the margins. And at the margins, the economic gains are linear to the additional activity due to not having a lockdown, but the growth of the virus is exponential.

Then the fact that the virus persists longer means places without a lockdown that did not drastically reduce the spread of the disease continue suffering economically.