"I have not determined that (the fee). That was done by the crazy market," he told De Telegraaf.
"I know that expectations will be high, but that is not bad, because I also demand a lot from myself.
"I did not come here to finish, I am 28, feel good and I am ambitious."
He added, "I'm an Ajax fan, as a result, it may be even more exciting to win the title again."