I fail to see how people are laughing at Neil's math...it's dead on. Play a sine wave(continuous power) for more than 15-20 seconds and see what happens. By full power, I mean clamp the amp to see what kind of power it's putting out. Hell, Meade might not even need all of the power for his setup...maybe just 10-12k out of the 15k available, resulting is being able to use the amp longer for tones.
As stated earlier, the transient nature of music is what makes the 15k power rating possible.
I'd bet my life savings that after playing a sine wave for 30 seconds, or bass racing at full volume, a normal class D amp will lose a lower % of it's power than the RK15k would...it's simply not made to perform at continuous output for that long.