adjusting for inflation, that would then be 9.6 million Euro today.La Defense: 45 million francs in 1990
But on the videosleeve it states 4.5 million Pounds in 1990, which is 9.1 million Euro today.
The same goes for Houston: 5 million dollar in 1986 is 9.7 million dollar today.
So approx. 10 million are needed to host a decent JMJ "city in concert" spectacle.
I don't think we'll see a big outdoor concert anymore soon...