What copyright you are talking about that we have to PAY? O__O
It was just a line of logo/symbol/signature. Can just slap it on with a simple text tool.

I am aware there are copyrighted and trademark to buy for 'uniqueness' in business realm, but this is digital art we are talking about...?

I just found it weird that if I have done a traditional pencil sketch, the signature is a pixelate sig, isn't it weird? XD