Rob,
You have to look at the market. There are more buyers of classical music in my neighborhood but still the eligible pool with good TT is very small. Just how many classical music lovers with vinyl set up do you think you have in your neighborhood? If there are no collectible records in the lot, I would not go over 50 cents a disk. You have to guess what tax break the seller would get from donation to Good Will and at least cover that. Generally, genuine folks with their life's collection want their records to go to a person who will appreciate them.
FYI, a local record exchange (used vinyl store) has a sign on the door saying that they don't buy classical music.