Who can afford to live in these expensive Rock Creek Park homes ?

This might sound lame but here we go.

I live in an apartment on Connecticut Ave very close to Rock Creek Park, when I go for walking behind the building as in more east towards the park, there are many homes which cost 3 to 5 million dollars, some even costing more. As per Zillow none of them are on sale and some have been off market for very long time. I was always curious to know who are these people.

Is this old money ? People who bought decades ago ? How can they even afford property taxes on these things ? Or is it lawyers, lobbyists, doctors etc ? Or is it investors ?