>>22
You could chalk it up partly to economies of scale. The cheapest books are the Narutos and DBZs that sell enough to get into top100 lists of regular books. Tokyopop pretty much set the $10 unflipped standard everyone else followed, and carved out most of the shojo market for themselves. Dark Horse is focused mainly on mature seinen manga, so naturally their audience is smaller. However they also have cheaper stuff like the Oh My Goddess revised editions at $10.95.

>>23
I love Del Rey's translation notes but in terms of material quality some of the smaller houses like DrMaster and Infinity Studios are outpacing all of the major players, and at the same $10 price too.