That would fall in the territory I describe as fuzzy above. At a sufficiently low cost inaction begins to seem morally questionable. That is largely driven by intuition though and I'm skeptical of attempts to scale it up and draw moral conclusions. I believe there are reasons the intuition exists that do not scale up simply. In other words, scaling up from this to conclude that if a very small cost is obligatory to save a single person then a very large cost is obligatory to save a million people is faulty reasoning in my opinion.