there's a number of ways to do it. here's two: 1.) check your LFS and see what something comparable is going for there. then adjust accordingly 2.) check the second-hand tank store. alot of towns seem to have people who's love of aquaria has, shall we say, 'expanded'. to support their hobby they often open up their own shops and deal in alot of used merchandise. the one we have here has the best coffee in town (can you tell i visit him regularly).
umm,... on second thought... actually,... they're not worth a thing! just box them up and send them to me and i'll 'dispose' of them for you. <eg>