There's a few options that come to mind, none of them perfect. One basic one is to ask how much we should be spending on health care; the risk here is if you think there is counterfactual effective medical spending. Another is what we feel is the marginal cost to current medicine of an additional year of life or healthy life, which could also be compared to what people think that year or a life saved is worth. What percentage of the current investment in medicine has a substantial benefit to the patient? is a way to try and measure this directly rather than indirectly.