When mailing a care package or letter to someone in the military overseas, are the postal rates similar to mailing to a foreign country (in other words, really high)?

Someone I work with just sent an email that his son-in-law is stationed in Afghanistan, in the U.S. Army. He requested cards, letters or care packages be sent. I am totally willing and actually looking forward to sending some food items for this soldier. I am wondering, however, how expensive the postal rates could be. I know that to send something to London or other European city it’s mucho dinero. Is mailing something to a military base any cheaper? Or would it be just like sending something to Asia, as far as postal rates?