I bet the old Japanese DBZ dvd or hell even the videos contain less episodes than the US.
DBZ (episodes, not movies) was never released on any home format in Japan.
Anyways, Futurama/Simpsons, anything like that has the backing of a major corperation like FOX, while DBZ/FMA/whatever has a small, small company selling it. FUNi needs the $20 a DVD for a 200 some episode series like DBZ, just due to the large amount of money that goes into bringing it over here. The average anime licenser doesn't have the deepest pockets, FOX has money running out of it's pants.
And another thing, anime merchandise is much more common over in Japan, and the animators get a little bit of that (right? not to sure on that), plus money from sub-licenses in other places.
That probably won't make much since... but I'm tired, so, excuse the rambiling.
But if we need to complain about anything, it's people chargin $30 for a 2 episode FLCL DVD.