No prob! I noticed you were new, so I didn't know if you knew or not. ;) I try to help when I can! (If you have a liquor store near you, they give away boxes all the time--I snag some from them from time to time.)
well, 10 typical manga weigh less than 5lbs (i just weighed them on my scale at home), add on the box and Media Mail is still only 4.57 for anything up to 6lbs, or 4.15 for up to 5lbs (if you're box is light) ~ hope that helps! (^_^)v here's a rate schedule too if you wanna check yourself: http://pe.usps.com/text/dmm300/Notice123.htm#1189285
Yeah, the only thing is you have to put them in your own box (you can't use a priority mail box for it). But it's usually cheaper to ship books that way (especially if you're doing a lot at once). I'd estimate that 9 books in a box would be around 5 pounds, which would probably be around $6 or $7 to ship to someone in the US with Media Mail. (lol, I mail waaaaaaaaay too much stuff...)