“Lives saved don’t diminish in marginal utility”, as you have said, but maybe hiccups do? A single person in a group of 10 hiccuppers is not as unfortunate as a lone hiccupper standing with 9 other people who don’t have hiccups. So even if the total negative utility of 10 hiccuppers is worse than that of one hiccupper, it’s not 10 times worse.
Since the utility function doesn’t have to be linear function in the number of hiccuppers (it only has to be monotonic) there is no reason why it can’t be bounded, forever lower (in absolute value) than the value of a single human life.
“Lives saved don’t diminish in marginal utility”, as you have said, but maybe hiccups do? A single person in a group of 10 hiccuppers is not as unfortunate as a lone hiccupper standing with 9 other people who don’t have hiccups. So even if the total negative utility of 10 hiccuppers is worse than that of one hiccupper, it’s not 10 times worse.
Since the utility function doesn’t have to be linear function in the number of hiccuppers (it only has to be monotonic) there is no reason why it can’t be bounded, forever lower (in absolute value) than the value of a single human life.