But it's not quite fair to compare two different cities in an economy where only some cities are shut down. If New York shuts down but can still purchase goods

But it's not quite fair to compare two different cities in an economy where only some cities are shut down. If New York shuts down but can still purchase goods from LA, then that's a remarkably different situation than the entire country being shut down, which is essentially what is going on now. You cannot study the cities in isolation. They are not self-sufficient economies. It's possible that one city was able to isolate because it depended on the other cities to be working to receive its goods and to jump-start its economy after the isolation. These effects cannot be ignored, and are substantially different than today, when it's not just that most states are shut down but also that most countries are shut down (well the ones of economic significance, anyway).