Palace of Versailles.

Current estimates of the cost to construct this home run also at about 2 billion (conservative) and probably were actually at lot higher.

So calling your modern version the first billion dollar home are distorting the truth. Many times this has been attempted and several times homes on this scale have been constructed (although several have never been occupied by any living soul, sometime intentionally).

I'm sure several of these ancient (or just old) constructions were also considered very ugly at the time, so maybe there is hope and maybe we will appreciate the new building in time (if it manages to remain standing).