In addition to EBay, keep an eye out here, Oade Bros, and DAT-Heads. I know there are other forums, maybe a couple Yahoo groups as well, but am less familiar with them. $1300-1500 seems to be the going prices for used SKM140 kit incl. actives. New, no idea. I love the sound outta 140s > V3, in some respects more than my CMC64 > V3.
Great thing about used gear - if you get stuff now and find a deal on something else later, you can generally sell it for what you paid, or damn near it.