I was, personally, never enamored with the idea of nonintelligent undead as cheap labor. They can't make craft or profession checks because those are trained only skills, and skeletons and zombies just don't have skill points. As such, they work at the much less useful rate of 1 sp a day, which won't even pay off the cost of raising them from the dead for almost a year (and that's even assuming that they're 1 HD creatures, good for nothing else). What's more, this is simple manual labor. There is nothing produced by their efforts.
As such, Undead can, at best, play a role in an economy, but they can't spark anything like the industrial revolution.