Based on a search of staticice, this is by far the cheapest RND4410 available:
http://www.staticice.com.au/cgi-bin/search.cgi?q=RND4410&spo…
Obviously you may prefer to buy a diskless unit, but for 4TB straight out of the box, this is a pretty good option.
For $2200?? wow, why not make your own
Motherboard with gigabit (and 4 sata connections) - $140 (be generous)
CPU - $60 (or whatever you have lying around)
Case - Lian Li (on of the small ones) $150
PSU - $70
4 * 1.5TB HDD Sata = $800
FReeNAS = FRee
There you go, a 6TB NAS for $1220 (half the price and 50% bigger)
Also Ht were selling a 2TB nas for $400 a few weeks back.