You are likely right that any "lots of calories" estimates you hear for this are going to be overestimated, especially in their marketing materials. however, that doesn't mean it's not a good exercise!
What matters with an exercise isn't really the calories you burn; No matter if you choose something that burns 500 in an hour or 250, you're still aiming for the same rate of weight loss either way. So, you would just eat more to compensate for the more intense exercise. :)
What matters with an exercise is whether or not you enjoy it. Minute for minute, running is a higher calorie burner than most exercises, but if you hate to run, or *can't* run, what good does it do you? If you enjoy it, and can do it, then you'll stick with it longer.