Watzke feels their deal with Arsenal will be the striker's last big move of his career.
The Gunners splashed out €63m for the Gabon international last week and despite losing the experienced forward, Watzke says they can be happy with the money made.
"We've never had a bigger offer for him," said Watzke.
"He will not get sold any more. At most, if he's up to something, at some point again he'll go to China."