IMO, the estimates of 700-1000 were true a year ago, but given the fact that the monitor parts alone have been selling for that much recently, and the boards have been selling for $300+, I'd say that's on the low end.
Yes, there are barn finds, and people who have sitting in their basements, who are unaware of what they are worth, so it's possible to find them for less, but when you add up the value of the parts, 1200-1500 for a top-condition cab isn't outrageous, IMO.