Incarnadine is right (I fix printers for a living, so I should know..;) There's all sorts of 'tricks' to printing; sometimes they even make different sized dots, just to make life interesting..;)  i've seen up to 1200dpi (in the price point I work at; we don't have commercial art printers...well, not many, anyways..;), but 300-600 is about the norm for most laserjets/inkjets you would own.
 

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)