Lightedman's dead comment, in response to my, "The issue is that it's a lot easier to build or buy a kilovolt power supply that doesn't have adequate current limiting than one that does," said, "You can buy Van de Graaf generators all day long. Quarter-million volts minimum for $200."
While van de Graaff generators are indeed relatively affordable, and indeed some even cost less than US$200, a working microwave oven costs US$60, and a broken one can be had for under US$10. Furthermore, a safe van de Graaff generator is not actually capable of supplying enough current at the high voltage to operate a vacuum tube, while a deadly microwave-oven transformer is; and there are orders of magnitude more microwave ovens available.
While van de Graaff generators are indeed relatively affordable, and indeed some even cost less than US$200, a working microwave oven costs US$60, and a broken one can be had for under US$10. Furthermore, a safe van de Graaff generator is not actually capable of supplying enough current at the high voltage to operate a vacuum tube, while a deadly microwave-oven transformer is; and there are orders of magnitude more microwave ovens available.