I don't think it's the money, not in a vacuum. It's this....
[table]Year|WHIP|K/9
2006|0.776|9.9
2007|0.771|13.0
2008|0.952|10.0
2009|1.147|10.1
2010|1.200|6.6[/table]
...combined with a perception that the money he expects to get extended is predicated on performance from 2-3 years ago that isn't being delivered now.
If he can right the ship and perform like he did 2-3 years ago, I don't think money would be an obstacle, but it seems like his expectation doesn't match the reality of his current performance.
Conversely, "Moonball" Bard has an 0.840 WHIP with a 22/4 K/BB ratio in 16.2 IP. Those are the numbers Papelbon was putting up and is expecting to get paid for now (although he's not doing that anymore).
More than anything, I want Papelbon to revert to the Papelbon of old, the one that resides in everyone's mind right now when they incorrectly refer to him as a still "dominant" closer, and to get paid for it. But, if I'm playing and paying the person based on what I think they will do for me from this point forward, Bard is the choice based on trends. Hopefully that changes, not the part about Bard being good, but the part about Papelbon slipping. Overall, that would be best for the team.