I believe it's authentic. Having said that, considering the age, condition of the zippers, what looks like stains on the handle, I think bidding has already reached top dollar for this bag. In addition, seller's feedback isn't very good; the neutrals and negatives have to do with poor communication and follow-up with customers. One of my criticisms of the listing is that the condition isn't fully described; it just says "good condition". From the photos, there are details that should be explained.
Price is always an individual viewpoint. I'm just saying from my experience and what I've seen on eBay, this bag isn't worth much more than the current high bid. Others may disagree with me.