A TECH-SAVVY New Yorker has made a whopping $21,000 by selling 3D-printed guns.The man, who identified himself as 'Kem', sold 110 guns to the attorney general's office in a buy-back scheme, Futurism reported.Earlier this year, the state of New York started a 'Cash for Guns' program that offers at least $200 to anyone who surrenders a gun. Kem then saw people tweeting about the program while joking that they could 3D-print guns to earn some instant cash.The tweets inspired Kem to try the scheme out in real life, using a $200 3D printer he'd gotten for Christmas."I 3D-printed a bunch...