I guess their overseas policy hurts them a bit. Paying a hefty premium for a pair of Grados doesn't probably seem that appealing to people outside US.
I'm personally really happy with Grado products. They got me into this hi-fi thing. :)
I suppose it might have something to do with trends and marketing as well. Perhaps that's a part of their niche appeal. It probably takes a certain kind of person to truly like Grado and their design. ;)