It costs a lot, unfortunately. Sequencing is still fairly expensive, and the methods in OP are fairly complex on top of that. There's also the interesting ques

It costs a lot, unfortunately. Sequencing is still fairly expensive, and the methods in OP are fairly complex on top of that. There's also the interesting question of: if the test came back positive in a seemingly-healthy control, how would you know if that was a true positive or a false positive? It's still early in the game as to how to work up a cancer detected only in blood. The gold standard is tissue biopsy, but how far are you willing to go to hunt that down? It's a tough one. Source: My spouse is one of the authors of the study in question.