I don't know how much they retailed for when new but I can give you some info that may help. Leisurepro sells the Air Z Nitrox for $600 at the moment; as a way of comparison, they sell the newer model Smart Tec for $1000. The usual conditions (grey market gear, no warranty, etc) apply but you weren't looking to buy new from an LDS anyway. I bought mine exactly like your situation: new, never used.
Actually, mine was a replacement for an Air X (previous model) that malfunctioned and Uwatec just replaced it with an Air Z Nitrox, the person who sold it to me was getting out of diving so never used it. I paid $400 for mine including the transmitter; I don't know how cheap that is but it seemed that way to me.
One thing to bear in mind about the Uwatecs is the inability to change the batteries yourself. You have to factor in that cost in the long-run, and that probably varies by LDS. If it still makes sense to you, do it.
There are also various pros and cons to this particular model. I don't regret buying mine, especially since this was my first dive computer, but I will probably be replacing it in the future. You can search on the board here for previous discussions.