I might roll your statement back a little bit but you're pretty much right. It's the vesting option for 2016 that's the killer. He gets $13M guaranteed if he finishes 48 games this year.
Some team might be wiling to pay around $15M total for him, but that's with giving up nothing, essentially his FA value (comp Balfour, K-Rod, and Romo). So at a minimum I think Philly needs to eat about $11M (including what they've already paid him this year) to get rid of him, and that's just to save money, so they wouldn't get any players back.