Answer:
A 1974 bus in reasonably good condition with a health motor that isn't a rusted pig should fetch $2500-$4000. Add a little if on the east coast; Deduct if an automatic (which are complete bastards and should have never been made.) A show/prestine version with all the goodies could get as high as $6000-8000, especially a Westfalia. 1974s aren't particularly sought after, but with the number of good split window buses dwindling, the Bay window buses are sure to have their day.