Erik they are worth what ever you value you them at.... If you want to make a killing on them sell them for $50.00 a pop... If you want to help some poor beginner , give them away... or find a price some where in between,you can live with... Mine I sold for what I paid for them... I read each one once or twice then put them on the shelf...There they have sat, some since '95. I saw them as a tool not an investment, so finally passed them on for someones elses use.
Barry