Sadly if he bought it from a retail chain thats about what he paid.
type Rs -229 each, around 500 with tax id guess
Box - 150
Cap - 150
Amp - 300
So about 1100
Probably around 300 for the install, too. 80 bucks to install a mono amp, 50 to put the subs in the box and sit the box in the trunk, probably an extra 100 to install the capacitor. Best buy FTL.
1400$
Seen it happen a few times, then i started stealing customers and making my own money by telling them how i could do everything for an assload cheaper. Lulz.