Yes, they're fair, but I recommend also getting a second quote from a comic book store.
I can't say whether they are fair. But, they are a business and they need to make money out of the buy-back. They are likely reasonable at the buy-back (they want to keep your business). If you think you can get a better offer elsewhere, I think you should definetly go that route!
Fair trade but comic books will do better with a collector
I agree with Gabriel's comment
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