Wenger signed the German international last season in a £42.5m deal from Real Madrid, smashing his side's transfer record in the process.
Wenger told reporters: "I would pay the money again. Of course. You expect the team to play well and not to put the responsibility on any one player to be a magician that does not exist any more in the modern game.
"Of course I have to get the best out of him because of his price. But I feel that responsibility exactly the same for a player who cost £1. He did not pay the £42m himself.
"When I see a talent, for any player, I think how can I get the best out of him. That is not linked with price. It is just a coincidence that the market is like it is."
Arsenal face Aston Villa in their Premier League clash later today.