It was (essential) bought by the Abu Dhabi Tourism board to be displayed at the Louvre Abu Dhabi. Basically they bought it as an expensive advertising campaign for their big shiny new museum
$500,000,000 for a week of advertising for a museum?
I think the only thing they are advertising is they have a lot of money.
I'm guessing targeting other people with a lot of money.
How many people a year go to the 'real' Louvre year after year just to see the Mona Lisa? I guess they're hoping for a similar long term pay off.