It's really hard to break into it. Being accurate enough to print at 300dpi is very difficult, and that's not particularly impressive. If it's color, then the problems are multiplied. You have to precisely align four different print heads (minimum), and the ink needs to be mixed just right for accurate colors.

This is also why you don't see open source 2d printers like you do for 3d printers. On the surface, adding a third dimension seems like it'd make things more complicated, but 3d printers don't need the level of accuracy that 2d printers do.