Here is how these purchases are described by the team who made the video:

Private Islands are an invitation to dream and linger, a place to escape the hustle and bustle and strains of everyday life. The surrounding water creates a natural boundary that provides private island dwellers with a freedom not found in any piece of real estate on the mainland. It is like having your own castle protected by the nature’s own moat.

Despite these unique characteristics, there is also a reverse side to the current conventional market of Private Islands. Many Private islands are too isolated and therefore difficult to reach, the construction and maintenance of the facilities are very expensive, they are threatened by rising sea levels and the rarity causes the problem that the demand outweighs the supply.

If nothing else this is a sign of the times.  I wonder if ther will ever have an economy version of these things 😉

thanks to elitetraveler.com for the great info