Those Lieberts are *fairly* plentiful on Ebay. The one I got (mentioned in Doug's post, page one) retailed for something like $1100-$1200, and I got it for $135, with shipping. A few days after I got mine, another ACer got the model below it for real cheap. When I was looking, there were several models up for sale.
Not only are they great UPS units, as it turns out, they clean the power quite nicely too due to the circuit topology.
Bob