well it retails from crutchfield for $360, the stuff I get from my wholesaler varies from 40%-50% (even 60% on crap products lol).
40% off of that amp is $216 so you got a good deal. Its better than paying $360 isn't it?
Shops may get the stuff cheaper, they may actually get it direct from the manufacturer in which its probably 60% less than retail. Markup is INSANE on electronics.