So yes, we can and we do 'objectively' (as in, per a standardized methodology) assign value to human suffering.
In your model, given certain starting conditions, can you ever get a positive value for human suffering? For example if rich people are willing to pay to see gladiators fight animals to the death, or just to see the poor people subjugated as slaves. I am pretty sure you assign positive financial value to animal suffering because factory farms torture animals to save a buck and therefore in purely economic terms they are doing "better".
If you could produce more meat cheaper at the expense of keeping animals in terrible conditions on factory farms, would you do it? After all, if money is all that matters the animal's suffering doesn't even enter the equation.
How about increasing financial gain at the expense of destroying the natural environment (eg overfishing, dumping plastics and releasing all the carbon from the ground)? Grandchildren may have to pay the bill, but what if you had perfect knowledge and knew they'd be economically richer, but with worse health outcomes and lots of species gone exinct?
Measuring implies a model, and the model makes assumptions about the world that may not be true, and the whole combination can be extremely harmful. Not to mention very human-centric (and "us" centric). As the Native American chief said:
When the Last Tree Is Cut Down, the Last Fish Eaten, and the Last Stream Poisoned, You Will Realize That You Cannot Eat Money
It's pretty common thing around here to see "the business case for doing [ethical thing]", as if being good business is a prerequisite to ethical behavior. It's particular disconcerting when it's applied to widespread problems.
Basic workplace safety is good... because it leads to higher returns on investment.
Discrimination is bad... because there's more money in equality.
Don't fuck over your employees... because you get better productivity that way.
It's a point of view that's pretty foreign to me.
