He said: "It is unbelievable how much has been spent. It looks like the banks are being very generous this year! I have been very surprised but then you know that there is a lot of money out there and on my front, I am just looking to develop the players we have here.
"Just in central midfield, for example, we have (Abou) Diaby, Denilson, (Cesc) Fabregas, (Mathieu) Flamini and Gilberto.
"All of these players are on their way up. They are not over the hill. Their level is still rising and they are getting better and better."
Chelsea have signed largely free transfers but have still splashed out £14m on winger Florent Malouda.
And Spurs have claimed a place at the top table with swoops for £10m Gareth Bale and £16.5m Darren Bent.
But Wenger is unmoved and insisted: "The challenge is the same. They can only play 11 players at the start of the game.
"And it is not necessarily the case that because they spend £50m that they are any better.
"Whenever I look at a potential new player the question I always ask myself: 'Is he good enough to win the league?'.
"If I come to the conclusion that he isn't, then I don't buy him."