Razer Mice/Trackballs - PriceGrabber.com
The Diamondback is the oldest model listed, and is the cheapest.
The Krait is like the Diamondback/Copperhead without the side buttons.
The Pro Solutions is basically a white Death Adder.
The Death Adder is actually cheaper than the Copperhead, which surprised me. The Copperhead is the older of the two.
The Lachesis sits at the end of the list, as it is the latest version and still rather expensive.
The ones listed out of sequence have a used/refurb in the listing, but the rest are the same price as the other listings of the same kind.