Nice smoking!
Group decision-making is of particular interest to me, so I nerded out and tracked the numbers.
In case anyone else is interested, here's the low, high, and average guesses for each category along with the correct answer and its difference from the average guess.
A (38 guesses) 47, 180*, 103.84, 255, (151.16)
B (12 guesses) 237, 818, 498.25, 736, (237.75)
C (18 guesses) 277, 1030, 577.69, 991, (413.31)
For this type of task where everyone generally has the same frames of reference, relevant experience and insight, etc., the correct answer is often very close to the group's average. That wasn't the case here. As a group, we really underestimated things.
*The highest guess for Category A was the winning entry.