But Allofs said it makes “no sense” to talk about whether those sums would be enough because the club had still not received any offers.
“We don’t have a game plan for ‘what would happen if,” he told German TV channel Sport 1.
“If someone comes with that much money… it’s not happened yet so we don’t need to think about it.
“But Kevin is also categorised as not for sale. I think he played a decisive role for our team last year. When you have the sporting ambition that we have, it should be forbidden to let him go.”