Definitely a good buy depending on condition, but I would bargain. I never pay what they ask at consignment. I would bring cash and offer it that way. As long as you know it is authentic and you don't see any problem... cash talks. Depending where you live it is not like everyday someone will walk in to throw down cash for that expensive of a bag unless that shop is known for having bags like that regularly. My 2 cents.
My big concern would be authenticity. Real bags are surely out there, it's just hard to verify their authenticity. If I bought it, I'd like to have a warranty or statement of guarantee from the consignment store and seller, if only for as long as it took me to get it to an Hermes boutique to have it authenticated. And I'm no expert, but apparently the only way to authenticate it is to send it in for service.
Sometimes when things are on consignment the store is in good relations with the owner of the item. (since they are trying to sell it etc.) Maybe you should ask if the owner can produce the receipt for the consignment shop owner to verify the authenticity for you. It is a thought and quite possible.
Long ago I brought several items to a consignment shop and they were very particular of details where their records were concerned.
Well, as it's a consignement store, I would suppose that the owner got it from one of her customers... This store doesn't just sell any old/second hand crap. It's designer clothing and accessories only.
Also, I live in Paris, so I don't think it would be unheard if a consignment store got a Birkin there.
Like I said earlier...ask the owner...they will most likely have records and possible verify authenticity through the owner. I liv ine an area where there are upscale consignments and you would be surprised what they can do for you. Also, it is a huge business here with designer high end bags and clothes. Ask.
If your answer is yes to both, then I'll say go for it!
If you're not in love with it at first sight, I think you should think it over. Although $7.5k seems like a bargain for an ostrich birkin, it is still a major purchase. It should be something that you'd love & feel totally comfortable with...something that you'll use a lot!