Panetta claims route closures through Pakistan costs U.S. 100 million per month
While strictly speaking this may be true the U.S. has not paid Pakistan for cost associated with its own efforts in the tribal areas since 2010. The amount is estimated by Pakistan at over 3 billion U.S. and even by the U.S. as over a billion. The U.S. has also cut other aid. These sums owing are used as leverage to force Pakistan to reopen the routes.
Panetta was speaking before a Senate Appropriations panel. The panel was discussing whether to cut even more aid to Pakistan. While Panetta urged the group not to cut the aid fully he said that conditions should be put on the 3.5 billion aid that is supposed to go to Pakistan this year.
The Pakistan government has demanded an apology for an attack on the border that killed 24 Pakistani troops and the cessation of drone attacks as a condition for reopening borders. The U.S. has said it will do neither.
U.S. officials urge Pakistan to simply reopen the routes without conditions. However, at the very least the Pakistanis are demanding a considerable increase in fees and no doubt the release of aid money. However Pakistan in all probability will settle for money and forget about the drone attack and apology conditions. See for example this article. The Pakistani foreign minister Hina Khar rejected the complaint by the U.S about price gouging. However there was no mention of the specific conditions supposedly required for reopening the routes that is the apology and the cessation of drone attacks. For more see this article.