SCOTTSDALE, Ariz. — When classic cars hit the auction block these days, $3 million seems to be the new $10 million.

As the global economy has endured a trade war and other uncertainties, some of the exuberance in this billion-dollar business, which surged after the last recession, is showing signs of ebbing. The Arizona Auction Week, one of the market’s two annual tent-pole events, just completed its mid-January run with sales down 3 percent from last year.

That drop was nowhere near as disastrous as the 34 percent slide at the industry’s other tent-pole extravaganza, last August in Monterey, Calif. But the falloff in Arizona to $244 million, from $251 million in 2019, still felt ominous.