Assuming the managers salaries vary similarly to the players salaries, if he moved to a championship club he could expect to earn 4-5 times what he's on in Sweden.
Say he gets a 3 year contract and even if he's a failure he'll earn what he earns in 12-15 years in Sweden.
Chances are another club would give him a go even then.
I don't think I could turn down that kind of money.
Not sure exactly how far his stock has risen, but if a premier league club comes knocking next then the pay difference becomes a lot bigger maybe 10-20 (my estimates) times what he is on now.