True, but again, if there exist people who currently rely on street parking and your solution is to raise prices so that new residents could compete for street parking then this still affects old residents. Gentrification is an externality too.

I am not saying we should stop doing everything that has externalities -- clearly we can't do that. It's just important to know that these transactions are not "between consenting adults" that dont affect others. Just because an owner of some land, some developers, and some perspective tenants agree on something doesn't mean it wont negatively affect a bunch of other people. And ignoring a bunch of other people entirely is not the correct choice.