BASEL, Switzerland — Some say there are too many international art fairs — nearly 300, according to one recent report — but there is little doubt that they are the most convenient way for the wealthy to get involved in the contemporary art market.

Art Basel, whose 50th edition previewed in Switzerland this past week, is the most significant fair of them all, with leading dealers offering their most important works to their biggest-spending clients. The event typically draws about 90,000 visitors, with a higher proportion of serious collectors and curators in Venice Biennale years such as this; 290 galleries were hoping to take advantage.

“Basel will always be Basel. Everyone comes here,” said Rolf A. Hoff, a Norwegian collector with a private museum in the Lofoten Islands. “There are so many good things. If you want a nice piece by an artist, you’ll find it. But it has always been expensive.”

“Basel Week,” like the week of the Frieze fair in London, is one of the few moments when the curtains part to reveal what is happening in the so-called primary market — the closely guarded trade in artworks sold by galleries for the first time. We can also find out what dealers are charging when they re-offer pieces. That glimpse can tell us where collectors’ tastes — and their money — are heading.