If the investment is good enough but prudent enough, the result may wind up proving the EMdrive will not work, while still making some useful discoveries along the way, that could apply to space vehicle propulsion or some unrelated matter. That is what good science does many times. Unexpected results and even accidents sometimes make for scientific revelations.
We do not know what we do not know.
Much scientific advancement has occurred while attempting to explain small inconsistencies in the data.