There is no excuse for the seller's misrepresentation of the bag's condition (new with tags), but fortunately it doesn't seem to be in the 'gum/peanut butter' condition.
So my first priority would be confirming its authenticity.
If the bag is authentic, you may want to have in consideration that you have paid about 1/2 of its original price, which seems a fair price for a pre-owned bal with modest signs of wear and tear IMO. (Tough decision
)
If the seller is not agreeable to provide your requested partial refund, I believe you can return it based on 'Item I received is not as described', following all ebay and expert TPF instructions. Good luck with your decision.