Late reply, but here's your answer. The satellite has twenty four 36 MHz transponders, yet the bandwidth is only 500 MHz. So, where does the other 364 MHz go? The transponders overlap. On a typical bird, you have transponder 14 at 11980, 15 at 12000, and 16 at 12020. Those are the center frequencies. The transponder is 36 MHz wide, so add and subtract 18 MHz to each center frequency and you get T14 at 11962-11998, T15 at 11982-12018 and T16 from 12002-12038. So you see that you have an overlap from 12002 to 12018 where there are signals on both the vertical and horizontal polarities.
That is why polarization of your LNB is so critical these days. You will have a 16 MHz overlap at each end of the transponder, except of course for T1 and T24. And, yes, the providers get premium rates for the middle four MHz and the two end transponders.