The Red Sox are apparently aiming high when it comes to compensation for Theo Epstein.
Consider that the first good move in Ben Cherington's tenure as Boston's GM--even if he hasn't officially been given the position yet.
While trades involving front-office personnel aren't exactly common, there's no reason why the Sox shouldn't view this the same as any deal for a player with one year left on their deal. And quite frankly, Theo is one of the best at his position, and effects more than any one player does when it comes to his team's success on the field.
As pointed out by Peter Abraham earlier today, baseball etiquette requires only that the Sox allow Theo to talk to the Cubs; nowhere does it say that they have to let him go for whatever scraps the Cubs are willing to toss in their direction. And in a situation like this, where the Sox are bargaining from a position of much greater strength, they'd be fools to accept anything short of a fortune in Chicago's first offer.
After all, the Sox can live with bringing Theo back for a year and they can deal with not having him running the show right now. They know who's going to step in for him. For Chicago, there's a void at GM which needs to be filled before free agency and the like starts in earnest.
The most the Red Sox stand to lose is any package the Cubs have already offered--one which the Sox have deemed unacceptable. The Cubs, on the other hand, stand to lose an entire offseason. If the Sox don't string 'em along in order to get the best deal possible, then they're not doing their jobs.