Most of the 3d printed objects I see for sale and made by 3d printer are parts for 3d printers themselves. Things like quadcopter frames are also very popular, because there simply isn't a manufacturing base yet for the kind of parts that people want. If something is popular enough, traditional businesses pick it up and render the 3d printed versions obsolete.
The trick for selling 3d prints, in my mind, is to either stay ahead of the traditional manufacturers by printing designs on the cutting edge or to look for small, individual goods that aren't known well enough to generate the investment necessary to make traditional manufacture feasible.
One business I've seen doing okay is places who set up cameras and take photographs of a person from multiple angles, then use the data to 3d print a little model of that person. Seems popular for gifts.
SD3 w/ RUMBA (8825s), merlin hot end (in pieces). Ender3 w/ silent board for PLA printing. Ender5 w/ silent board, e3d v6, new z lead screw, and glass bed. DiY Kossel w/ smoothieboard (in pieces). Vellman Vertex (in pieces)
Shapeoko2 router in process of being converted to laser engraver (in pieces)
Multicam 5000 series CNC Router w/ 11HP spindle, 5x10' table, and auto tool changer (in pieces)
. Just google it.