Sketch Up would not be a good option because it produces mesh models which look like garbage when printed, a good low cost Nurbs modeling software that produces true curves for digital fabrication would be Rhino 3d. The educational version of Rhino is $195. http://www.rhino3d.com/

Edit: and if you want to make your cups parametric like the examples the grasshopper plugin for Rhino is the way to go http://www.grasshopper3d.com/