This switch seems irrational/unnecessary for most career paths, given that the cost is 2-3 more years invested into largely irrelevant work or coursework. You might have your own reasons to do it, but I don't think you'll find many previous examples of students making this switch, which makes it all the more harder to find relevant advice. Are you sure your current PhD program isn't working out for you? Are you sure a top 15 econ PhD program *would* work out for you? (because if not, it's much easier to stay on the current path and find an industry job in 3 years rather than to switch and eventually arrive at the same outcome)