What economic damage can be done in the interval between a private key being accessed by a criminal and the key being revoked?

Depends on the systems connected to the private key of course, but billions per incident are certainly possible in some cases.

Even if this is just private chat on messenger platforms rather than 2FA or HTTPS, imagine how blackmailers would respond to getting all the nudes, the drunk confessions, the adultery, from 30 minutes access to all of the 10th most popular chat app in your country.