Well it should be whatever he's worth in relation to his level, age, experience and importance to the club but I wouldn't think it absurd if he signed a deal to make him a top 10 earner in Europe.
Obviously we can only take the figures thrown about with a pinch of salt and maybe the 400k you hear from China etc aren't sustainable but he's definitely in the 250k+ bracket for me.
I'd like to think otherwise but I think the "wage structure" is still in effect. Our earnings have gone up a lot and so have our top earners (I think Cesc was around 100k and now our top boys are around 140k) and around 180k sounds like the kind of arbitrary limit we'd have in place for 2017. I just can't see us offering players 140k in 2014 and then 250k in 2017.
That wage structure wasn't just to save money during adversity, it felt more like a socialist policy and players like Coquelin getting a reported 75k doesn't feel far from Diaby/Denilson getting 50k so it makes me think we're still in that place.
Going over 250k would be a big jump for Arsenal, but if it's a case of keep or lose him for say 300, I think he'd be worth it. I think there's a difference between a big signing and someone who's already proved they're a key player for you and we should be fighting to do what we can. It would give a bigger boost to the club than any big signing would imo.
But like you say, maybe we are willing to stretch and maybe he's just being an arse about it . I guess we won't find out until next year what really happened.