The guy just has no clue or appreciation for this type of thing. There are supposed to be several samurai swords in the house as well. My dad has offered to help for free. I'm pushing him to push back on the neighbor a little more. God forbid you sell the house and a kid finds a hidden gun or sword and hurts themselves... Guilt may be the best approach
I'll definitely pass along the recommendations to my dad. He was thinking of offering around $300 for it. I'm sure he could probably get it for less, but he wants to be (somewhat) fair to the guy. It's that whole kharma thing. If you honestly think $300 is too high, then I'll tell him to offer less. Or at least factor in $100 or so into the price to have it cleaned.