Nahmad Family Made Billions Trading Art

They have 15,000 square feet of a duty-free building next to the airport in Geneva.
The warehouse contains between 4,500 and 5,000 works of art, worth somewhere between $3 billion and $4 billion. The Nahmads' has 300 Picassos, worth some $900 million. How they learn the trade? [from Forbes]

When the Nahmads play the game as buyers, they're willing to let things go. They buy for inventory and have enough money to sit and wait, so they only buy cheaply.
How about buy artworks from artists in their studios? It's extremely cheap comparing to auction houses.

R. Marinho paintings.