I bid on a mint condition frame and fork 2 years ago that ended up selling for $350. The prices were so high on eBay at that time that I gave up on the MB-1 and settled for an MB-2.
You should post the same question in the vintage forum at mtbr.com.
You can also watch what they're going for on eBay.
http://sporting-goods.search.ebay.co...MEFSRCHQ3aSRCH