“Four years after Steve Jobs introduced it, the iPad is Apple’s (AAPL) second biggest cash cow,” Philip Elmer-DeWitt reports for Fortune. “If the iPhone generates a bit more than $5 of every $10 Apple collects, the iPad brings in nearly $2. And for both products, the holiday quarter — the one that Apple reports next Monday — is the big one.”

“iPad sales are harder to estimate than the iPhone’s this time. The iPad Air didn’t ship until Nov. 1, missing one third of the quarter; the new iPad Mini (with Retina display) showed up 12 days later and was in short supply all the way through Christmas,” P.E.D. reports. “But we’ve managed to collect unit sales estimates from 45 Apple analysts — 28 professionals and 17 amateurs.”

“The average estimate among all the analysts is 25 million iPads, up 10% from the same quarter last year.,” P.E.D. reports. “Last year, the pros were right and the indies wrong. The consensus was 24 million iPads, with the pros at 22.8 million and the amateurs at 25.5 million. The correct number, according to Apple, was 22.86 iPads. We’ll find out who was closest to the mark this year when Apple reports its Q1 1014 earnings after the markets close on Monday, Jan. 27.”

See all 45 Apple analysts’ iPad unit sales estimates here.