When half an hour of sprints and run upstairs to pump my heart rate is still elevated and I may burn an extra 100 calories. But I think that for a male 400 is about right. I think of Pump as going to the bank and investing in CD's. The higher metabolism will pay off in fat burning dividends later in the day.
400 does sound about right for a male.
i'm a 5'3, 10.5 stone female and the most i've ever done is 520, and that was upping all my weights, and really pushing it (i.e super deep squats, low lunges).
The only thing i can think of with the 800 cals person, is maybe as they are new to the class, their body is still reacting to the differing exercises, are they overweight? If so they are likely to burn more calories than someone who is not, especially if very obese.
Calories burned is individual to the person - size, weight, fitness all play a part.
I havn't worn my HRM in Pump in ages as, as others have said, you will continue burning calories after the class.
I used to get about 650.
I get sweat dripping off my elbows in Squats.
This has been discussed a number of times before. Search the forum for the other threads.
Obviously the harder you work the more cals you burn. I also find that my heart rate gets higher when it is hotter in the studio, which means my HRM records a higher calorie burn even though I would have done the same weights.
My highest burn was about 750 cals but usually average around 700.