Italian players usually tend to be more 'loyal' to their teams and thus wouldn't jump ship unless the club wanted them out for their own good. Perfect example of that: Tacchi, Conte, Zambrotta and Maresca. That's why I think negotiaiting a deal with those players would be easy. Di Vaio and Del Piero only needed a couple of minutes to agree terms with Moggi. Whereas, Trezeguet and Davids probably wanted more than what is on offer.
We can't really judge about that too as we don't know the exact figures: what Juve offered the players and what the players wanted. But I think Trezeguet rightly deserves more (he currently nets the same as Iuliano!!).