Is this a knock off?

It probably is. A major sign is that there is no picture. If it is real and they would send it to you, there would be a picture to prove its identity. Second is the price. The price has to at least compare to the real price. It really doesn't. The only way someone would sell it for that price is because of its quality after its been used, and that would be proven in the picture. Don't fall for scams like this. It's illegal! Look up Fakes Are Never in Fashion. Some scary stuff goes on in illegal selling.