Hand-carved wooden ducks were assembled in neat rows on 380 tables filling the large hall. Ducks by the hundreds, by the thousands, glass eyes staring out at passersby.

“Has everybody got enough ducks to look at today?” asked collector Bill Claussen at a beginner’s decoy collecting seminar. “If not, you have an insatiable appetite.”

There were enough to go around for everyone. For the 35 people attending the seminar. For all of those attending the 39th annual National Antique Decoy and Sporting Collectibles Show last month.

The auction was an eye-opener.

In all, $4.3 million worth of carved ducks — seven of them going for six figures — were sold in two days.

The merchandise was hot and the numbers were large enough to boggle the minds of longtime collectors who took up the hobby when prices were lower and competition to find rare decoys was less intense.

Donna Tonelli of Spring Valley, Ill., a veteran collector, told of acquiring ducks for $5 or $10 in the 1960s that now sell for $20,000. She sold one decoy for $150 that would go for $90,000 now, she said.

“But we had fun,” she said.

Herb Desch of Chicago, president of the 1,100-member Midwest Decoy Collectors Association, said he is a longtime duck hunter, but initially didn’t consider collecting decoys. He used to accompany his wife on her antique hunting trips and hated it.

“(It) was like root canal,” Desch said. “She said, ‘You need a hobby’ and bought me a decoy for $5. It’s addictive.”

Expensive, too, if a collector gets serious. One reason, as Desch and Tonelli noted, is that carvers of the past, who thought of themselves as making practical implements for their own duck hunting, have come to be seen as folk artists.

There are many ways to collect decoys, but all experts agree a collector should specialize in duck types (mallards, pintails or blue teal), factory-made decoys, or in regions such as the Illinois River Valley, Wisconsin or New England.

“Don’t try to collect everything,” said Roger Ludwig, a 40-year collector from Oshkosh, Wis. “You have to stay focused.”

Of course, collectors may make resolutions and then waver, as in where to draw the line on price.

“You might say, ‘I’ll never pay more than $1,000 for a bird,”‘ Ludwig said, “and the next thing you know you’re spending $5,000.”