Do you know exactly which one he got?
Don't know the actual prices you saw and if they're reasonable but in general an extra $300 for a DD is money well spent.
it was the difference between about $940 for the DPMS Panther AP4 and $1200ish for the DD, not sure exactly what model though. Chamber was not chrome lined, not sure about the barrel. Both come with removable rear and fixed front sights. If I did go DPMS I'd probably end up jacking the price up anyway adding chromed barrel, bore, and chamber.