I'm guessing what he means is no splicing or drilling of YOUR OWN stuff. The speaker is obviously cut and drilled into the dash piece he supplies, but you don't have to hack up your own stuff. If I understand correctly, you just pop out your upper dash pieces (and stash them away neatly) and snap in his upper dash pieces with the speakers and power button and everything already cut in. Run the wires he supplies to the amp, stash the amp somewhere, plug the extra cord into the headphone jack of your MP3 player and away you go.
After reading Merlot's comment, I started trying to source upper dash pieces, the 4" Kappa series speakers and a decent, low draw 150 watt amp. If you found the dash pieces used, got a good deal on the speakers, bought the power switch from Radio Shack or whatever, found a decent deal on an amp, and did all of your own labor (cutting, wiring, etc) you could probably save $150. But for some people, it's worth $150 not to have to jack with it.
I won't ride with headphones because I'm concerned it will drown out TOO much noise around me. And I like to hear what's going on. But that Busasounds setup (assuming the amp/speaker quality is decent) would be a reasonable compromise. You could listen to music, but you'd still hear everything around you.
Not sure I'd do it to my bike, but I don't think it's ridiculous or anything.