Yes, by using a model. The assumptions of the model are subjective in the sense of making judgments about what's important. For example, they don't take into account catastrophic collapse of the environment (overfishing, species extinction, ecological collapse eg from bees dying out, acidification of oceans from CO2 release). They also make assumptions about people's utility functions -- the famous example by Bill Gates that baldness has much more more research being done on it than malaria relative to the suffering, because people with more money speak with a larger economic voice and skew the results.
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".