Drobo has a couple of rebate deals going on right now that will net you a $239 price on the base model after rebate.
The 4-bay Drobo (USB 2.0/Firewire 800) runs $289 normally at B&H, but has a $50 mail-in rebate available through Sept. 30.
The 5-bay Drobo FS network drive runs $599, but has a $100 mail-in rebate (thru 9/30) that nets you a $499 final price.
The 5-bay Drobo S (USB 3.0/eSata/Firewire 800) runs $694 normally, but also has a $100 mail-in rebate for a $594 net cost.
Hit any of the above links to B&H Photo for more details.