Yes, 10 ETH is alot of money but i would agree with him it's your fault to send to wrong address.
I'm not disputing that it is my fault. This is a common problem on many exchanges. They can retrieve the ETH if they wanted to. Read the posts below to see examples of users claiming they received their ETH back.
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Can you show the proof of this?
Here are some policies of exchanges who can recover mistakes like this: