You likely won't get much out of them wherever you go. I was in Half Price Books not long ago, and they had what seemed to be the entire collection of TNG Columbia House tapes - at least 80 of the tapes, anyway - and they were selling them at two dollars per tape.
Now you know, any store like that has to mark something up to get a profit out of things. It makes me wonder if the person who sold them even got ten dollars out of the whole collection.
As already said in this thread, people have moved on to DVDs, Blu-Ray, and Netflix. What took up an entire shelving unit on tape can now fit in about a Subway footlong-size space on one shelf on DVD ... Or none at all if you stream through Netflix.