Wenger, whose Gunners team have not won a trophy for eight years and lost the services of the likes of Cesc Fabregas and Robin van Persie during that period, has often faced criticism that he has not been prepared to pay out major fees for players.
Germany international Ozil has been in sparkling form for the north London outfit since then, helping them to the top of the Barclays Premier League.
Asked if he had been at all wary of spending so much on one player, Wenger told arsenal.com: "Of course, it's a big responsibility to spend that amount of money.
"But I feel comfortable with it because we had the money to do it.
"Before we couldn't have done it because we didn't have the money available. It's as simple as that.
"I had a huge sense of responsibility when we built the (Emirates) stadium (which opened in 2006) to get the club through it without going bankrupt.
"The first years were difficult, and also explained why we lost some players.
"Now we are in a more comfortable financial position, I - more than anyone - want the great players to play for Arsenal Football Club.