If it's something you want and a price you're willing to pay, then it's a good deal for you. A quick check on www.GunsAmerica.com
showed that the $400 you agreed to is pretty much in line with how the few listed there were priced.
I am not a collector of cutaways, replicas, dummy guns, or anything else like that, so I wouldn't have bought it.
I know that some cutaways can be very collectible, but I somewhat doubt that CZ cutaways are particularly collectible in the U.S.A. If you ever decide to sell it, an auction house in Europe would probably bring you the most money for it. Of course, you'd have to have a licensed exporter send it for you, so it may be cost-prohibitive on that basis.