A CNC engraving machine, fully assembled, new in box, $200, about 5 years ago at MicroCenter. It kinda worked, but the work area was really small 16 x 10 cm, and the motor left a lot to be desired.
The state of the art back then sucked.... now I'm pondering something a bit better, like the Carvera Air.
Before that, Turbo Pascal for $49 was amazing.