...
You sure? His contract runs till 2016 (renewed earlier this year) and he earns more than Buffon iirc.
you sure?

... As good as Ivanovic is, he is not a fundamental player for them and for much of his time there was more of a bench player than a sure starter, at least initially. Even after he began to start more regularly and eventually became a 1st team regular, he was always one of the first to be left out if there was to be a tactical change or something.
Not saying he is not a good player, but he is not as important to the team as Terry, Lampard, Essien, Drogba, who have been Chelsea's truly irreplaceable players ... and the ones, who are surely getting paid better than Buffon.
Chelsea at one point were even looking to offload Ivcanovic, hence those links to Milan and Juve, and then they waited almost till the end of his old contract before they offered him extension - you just don't do this with indispensable players, who are the ones to cost a lot in transfer fees and command thru-the-roof salaries.
I tried looking for info on Ivanovic's salary and all I could find was that he was being paid ~3.5 mil (euros) which sounds about right, considering the above, and is likely well within Juve's budget.
Anyways, when I said he was not going to be overly expensive, I was referring mainly to the transfer fee and that is determined by the market, hype around the player and his current club's desire to keep him ... virtually all of the above factors, provided AVB is indeed looking to offload Ivanovic, are in favor of a relatively low transfer fee of around 15 mil, and even less than that if Juve prep the player and make him "want only Juve and no other team", which would give them leverage in the negotiations.
Milan's deal for Ibra was possible mainly due to Barca's desire to get rid of him, and his desire to go to Milan only ... you have these two, you have a great advantage in a negotiation.
Now, all that's left is to see how much Juve wants Ivanovic 'cause if AVB indeed is looking to get rid of him, there is no reason why they cannot get him at a pretty good price.