In reply to Enty:
You'll get complete wheelsets for around £2300, but if you build them yourself you can buy the hubs, rims & spokes for around £1950. your right probably more expensive than the Zipps (especially at the price youve been offered them!!) The CK hubs are crackin though and completely user serviceable. and when you brake a spoke you can replace it yourself without having to send it away like the factory built Mavics.
At the price you can get them i'd probably go with the ZIPPs, Are they for racing? I've got tubs on my TT bike and CX bike but never feel comfotable going a long way from home on a road bike with tubs and having to rely on some pitstop if I get a puncture. Plenty of people swear by them though and they are lighter.
A