FYI - I found the Central Wheel Components price list for wheel building, which will give a ball-park idea of costs...
http://www.central-wheel.co.uk/price_lists/classic_price_list.pdf (see second page)
Remember, if you get the dealer to do it under warranty, they'll only replace them like-for-like, so they will be galvanised and end up going the same way again at some point.