"Efficiency" meaning, given some input cost, reducing the loss of applying that cost, toward some measured outcomes. High efficiency implies something about each of those three stages, none of which are reasonable to apply in all situations:
1. That the only input to the system is cost/money (or proxies of that, like compensated human time). Put another way: That the model you're working with is perfectly liquid, and you don't need to worry about fundamental supply constraints.
2. That the loss is truly loss, and there isn't some knock-on effects from that loss which might range from generally beneficial and good, to actually being somewhat responsible for the output metric, and your model is measuring the wrong thing.
3. That the output metric correctly and holistically proxies for the real-world outcomes you desire.
Using the example from the article on standardized testing: A school administration might make an efficiency argument by comparing dollars spent to standardized test scores.
* Dollars isn't the only input to this system, however; two major ones also include the quality of teachers and home life of the students. Increasing the spend of the system might do nothing to standardized test scores if these two qualities also can't be improved (you might make the argument that increasing dollars attracts better teachers, and there's some truth to this, but generally (even in tech) these two things just aren't strongly correlated; many organizations have forgotten what it even means to be "good at your job" and how to screen for quality in interviews. When organizations lose that, no amount of money can generate good hires because the litmus test doing the hiring is bad).
* "Loss" in this system might be the increase of funding without seeing proportionally increasing test scores; which does not account for spending money in extracurriculars like music, art, and sports; all generally desirable things we believe money should be spent on (isn't it interesting that we call these things "extra"curriculars?).
* Even if a school administration can apply this model to increase test scores, increasing test scores might not be an outcome anyone really wants. As the article says, all that guarantees is a generation of great test-takers. Increasing college acceptance rates? We've guaranteed a generation of debtors and bad degrees. Turns out, its impossible to proxy for the real world thing you want, in a way that can be measured on a societal level.
All of this is really just symptoms of the "financialization of everything", which has been talked about endlessly. In particular to this discussion, society has broadly forgotten about what the word "service" means; that public transit in your city must be a capitalistic enterprise, it itself has an efficiency metric that must be internally positive, because the broader positive efficiency impact that public transit network has on the people and businesses in the city, and thus municipal tax income, is too complex to account for within a more unified economic model.