Every $1 invested in resilient infrastructure yields a $4 return in avoided recovery costs, according to case studies published by the World Bank and the Coalition for Disaster Resilient Infrastructure. FEMA estimates those cost savings can be even higher in the U. S. – and suggests federally funded climate mitigation grants “can save the nation $6 in future disaster costs for every $1 spent on hazard mitigation.”

Just saying.

Also cities change a lot. Only 35% of owner occupied housing in the US is older then 1969. Construction in the US is also an over $2trillion industry, so just changing new construction is a trillion dollar project.

I don't think that's a fair reading of the article, the three points it mentions are:

1. Invest in trees and green spaces. This ones achievable at a small scale.

2. Prevent new construction in risky places. This ones literally free because it's just not doing stuff that's harmful.

3. Employ nature-based and multipurpose facilities. I'll admit this one could end up being pricey.

Then it has a whole bit about how these policies could save money.

Either way, I'm not reading this as suggesting expensive rebuilds.