Hi,
I don't think you are dumb at all! You are just inexperienced & you are a nice person, thats why you believe people who say 'authentic' even when the item is not. Plenty of us have fallen for that many, many times darl!
ok, I've spent around 15 minutes comparing the pics. Now, before I say anything, I would just like to say that alot of major department stores & high end websites (like eluxury.com) get the a sample to photograph before teh product is finalised , so consequently, sometimes the pictures they show, differ from the real end product that is for sale, so that could be the case here. Unfortunately, there a several big diffrences between the ebay pictures & the BG pics.
The material does look like a sort of vinyl, not leather, but as someone else said, that could just be the lighting. The placement of the Jimmy choo logo plaque is lower on the ebay bag than the BG bag. The metal zipper tags are a different shape on the bags & the square metal decorations are very different. On the BG bag, they appear to be much more flat that the ebay pics.
Look at the shape of the bottom of the handles where it meets the main frame of the bag. On the BG bag, itsa very pronounced sqaure shape, on the ebay bag, its a lot more rounded when it turns int othe handle.
Look at the handle. On the BG bag there is clearly some sort of framework in the handle, this makes the handle its self a sort of 3D rounded handle. The handle on the ebay bag is completely flat. There is no molding at all.
I am not categorically saying its fake, I haven't seen this Choo bag IRL so I am no expert, but thes are just seom differences I have noticed from comparing the two.
Good luck with it, when it arrives, havea really, really good look over it & if it is fake, don't be afraid to go through paypal to get your money back.