I agree that the purse forum should be your first stop. Second, a Chinese seller of Chanel bags is a HUGE red flag. Why even take the risk? If the price is too good to be true, it IS too good to be true. Even individuals selling a used Chanel know what they have and what it is worth.
Either check with the purseforum and find a trusted reseller if you are looking to buy used, or buy new from a reputable location or site (major department store, Chanel, etc.). DO NOT spend that amount (whatever it is, it isn't going to be cheap) and just hope for the best. That's throwing money away.