'97s go for around $200, '98-03 go for $250-300, and '04s are $500-800. All this depends on condition. If the teflon coating is missing from the rotors, it can knock a lot off the price.
97's have a vacuum port next the the bypass valve. And lately they are going for much cheaper than that Ron. They are overpriced on ebay most of the time, but you can find any Gen 3 M90 for less than $200 on clubgp.