Touring bikes retain their value better than your average bike because the technology hasn't substantially changed. New touring bikes will still be all steel, with similar geometry, and similar components. A racing bike quickly drops value after a few years and then plateaus because racing technology changes so quickly (brifters, frame material, geometry, etc). Comparing this to a Varsity is also a mistake. Low end bike boom bikes maintain a minimum value because they retain basic functionality as a bicycle.