DD prices high online so people will buy from dealers. Lots of smaller companies do that to support the shops that carry them.From the link just posted JL seems cheaper than some of the door speaker pairs, Much less tha DD set, although the extra 200w rated power would be kind of nice if looking to replace a set of 8s.
Ironically, the inverse is true for larger brands, most shops(or at least the ones i've been to) way overcharge for kicker/rockford/jl products than can be found online for as much as $100 less in my experience.