Super did not assemble a 'cost/benefit' analysis.
Strictly speaking, c/b analysis has to do with measurable economic benefits.
There's no 'economic' consideration applicable when measuring the value of life. Similarly, there's no 'economic' consideration of the beauty of a sunset. More accurately, such 'benefit' cannot be measured in monetary terms, despite the wishes of the Singer/Pragmatist crowd.
Yes, but economics does not necessarily mean financial or monetary, as you assume. Economics, as a method of analysis, has been applied, quite successfully and importantly, in many non-financial and non-monetary areas, including Judge Posner's remarkable contribution in the 'economics of law' movement. Posner argues that not only human behavior, but law can be understood by the theory of wealth-maximization. This is the philosophy that individuals act in a way that will maximize their benefit (the results of their action) while minimizing cost (energy, time etc. expended in action.)
What Supercat was doing regarding the evaluation of potential treatments is an almost classic example of comparing the measurable benefits of a possible course of action (i.e. giving the medication or treatment) with the measurable costs of such a course of action (i.e. the detrimental effects of such a course of action). It is a useful way to make decisions and we all do it everyday.
As Supercat points out that is how we make decisions on continued treatment in cases of what we generally term "terminal illness." What I was refining with Supercat was the fact that he had not defined "terminal condition" as he contended, but had provided a sound recitation of the evaluative process of a proposed course of treatment.