Chelsea secured a £47.5m deal for the talented German forward, who will join the West London club on July 1.
"The entire Chelsea package in the end, however, turned out to be the best in my career. Money played a marginal role.
"For me, money was never a decisive factor, otherwise I could have gone to China. Chelsea is a leading club in European football. There is a team of great quality, we want to get to the top. I don't regret my decision for even a second."