The timing varies regardless if you send it regular mail or priority or whatever.
This is what I was told: The package leaves your post office and goes to a military holding place for mail. It can sit for a day or a few weeks, when they get a plane full the plane heads to Irag. From there it gets divided out to the different bases of operation. I sent a package regular post, a cousin sent one the same day, same time, same post office but used priority. I am sure hers got to NJ ahead of mine but they both got to our cousin in Irag at the same time.
At the time the begining they were taking over a month. When things leveled out it was about two weeks. Still it varies.
As for cost, I sent HEAVY boxes since I used hard candy for a filler. 12 x18 x 12 box??? or smaller, The most I think I ever paid was $12.00. I would just tell them sent it the cheapest way.
The lightest box I sent had two bags of chips and non refrigerated dip. The dip was tape to the bottom so it would not roll about and mush the chip. I used to send all sorts of weird stuff.