In a bizarre twist of circumstances I found myself in the company of two billionaires three years ago, really nice people two arms and legs same as the rest of us.
When the left one of their lackies tells me they where off to look at an estate abroad, as they where now so wealthy that they only bought stuff that wasn't being made anymore, i.e. had a finite supply, large tracts of land, Art, gold etc.
This was in an effort to cascade wealth through the generations, i.e. a Van Gogh may fall in value but in the next three or four generations there will be bubble opportunities to sell into.