Plus copper lines.

I bet you'll find something for $1,000 cash somewhere.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=220222002504
With lineset.

Or, http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=270226981681
Includes lineset and claims of a quick-connect flanged connections, meaning no need to evacuate with vacuum pump and adjust freon charge.

Apparently the pricing that you are getting, must be retail. Someone that you know, or someone that they know, might know of some A/C people. If so, you can get a better price buying it from a supply house, and then getting the actual A/C guy to, connect, evacuate and charge it. You can buy split system 4ton condenser units from about $600.00, and the inside air handler, for about $400.00 without heat.
I am with PBH on being able to get it for about a grand, cash.

4 ton condensing unit for $600? What brand? I've priced out 2.5 ton units for more than that (13-14 seer with copeland scroll compressor).

Do the window units use a lot of power? I would like something for the AZ summers but dont want my power bill going through the roof!

I don't think there can be a huge difference, but each unit you look at should have a SEER (IIRC) rating that will indicate efficiency. My guess is the higher quality split units are more energy efficient.