what's the catch on this RODI unit?

I've been looking at RODI units lately for a new reef tank setup, and
found the item listed below. Basically it's a 6 stage 100gpd unit for
$110. Seems like it's too good to be true, but I don't know enough about
these to tell if there's something fundamentally wrong with it. Can
anyone offer more expert insight? TIA

P.S. I hope my post isn't misconstrued as a feeble advertising attempt;
I swear I'm not affilitated with seller/store, I'm just some guy trying
not to get ripped off!

http://cgi.ebay.com/ws/eBayISAPI.dll...tegory=20 756