I completely forgot to mention that the Eagles made a point to mention that posting Hisashi Iwakuma was the exception, not the rule. That is to say, just because they're willing to post Iwakuma now, doesn't mean they'll be just as willing to post other players in the future. In addition, it seems Iwakuma spent time talking to the front office over a number of meetings to let them know just how much he wanted to pitch in the Majors.
There are, a couple of other things to consider. If this posting doesn't go as intended (read: the Eagles feel they aren't getting enough in return through bids), they get to keep Iwakuma and say that they at least tried. If Iwakuma does successfully get posted, then the Eagles are hoping Iwakuma will remember their good-will and return the favor by signing with the team when he returns to Japan.