I was looking for a while for one and finally found one for $189.00.
A very good price considering most of the" professionally" rebuilt units go for over $250.
Some sellers just pick these up from estates sales and you don't know what your getting. Some say they are rebuilt and they really don't have the experience to rebuild one you got to watch from who you buy from.
Have you ever worked with transformer before? you can pick up sometimes a good deal if your prepared to rebuild it.
If you do buy one first thing you should do is replace the power cord as they came with a cloth cord and there not very reliable.
Heres a link from the guy I got mine from. Watch his auctions but hold off from bidding till the end so you don't drive up the price. I sniped mine manually at the last 5 seconds after watching it for a week. I got to know what the other bidders would raise me by testing them.
This seller had a family flu problem and was a few days late shipping it. He refunded the shipping and included a bag of extra train goodies too. Also said free shipping on my next purchase no time limit too.
How big is your layout? With a zw you should be set easily to run 4 trains and power a lot of accessory's too.
This man likes to talk trains too so if you have a problem you can just give him a call. or if your in the Harrisburg Pa area he gives you his address too. He also sells train parts you can e mail him a request if your looking for that special part.