First off, I like Wenger and think he's been a genius in the transfer market in the past. He also gets his teams playing the most attractive football (IMO) in the league.
But the following just shows he's struggling to adapt to the modern transfer market:
http://news.bbc.co.uk/sport1/hi/football/14676338.stm
He seems to have the attitude that he alone should set the transfer value of players he's chasing, even if this flies in the face of the value the rest of the market believes. It's one thing to not be held to ransom by clubs wanting extortionate fees, but quite another to refuse to believe that there's been stupid transfer fee inflation in recent years (principally driven first by Chavski, then by Shiteh).
The irony is, he takes a completely different line when it's Arsenal players being targetted by other clubs, demanding the sort of giant transfer fee from other clubs that he baulks at paying.
Man U have paid £18m for Phil Jones, who's behind Cahill in terms of career development. Jones may or may not be better, long-term, but Cahill's nearer the finished article & has played for England already. Bolton will certainly be looking for a fee close to what Man U paid - and remember that Bolton neither need nor want to sell. Conversely, Wenger NEEDS a strong CB. And everyone knows he's just trousered £60m in fees from Nasri & Fabregas.
Of course, the current Cahill situation may just be posturing and Wenger will pay the big price the transfer needs. But the attitude of Wenger in the transfer market has seen Arsenal miss out on key players, leaving them too weak in crucial positions and consigned them to also-rans.
Absolutely, always good for development as a player when you regularly appear alongside Zat Knight.