Revealed preference is a good way to get a handle on what people value, but its normative foundation is strongest when the tradeoff is internal to people. Eg when we value lives vs income, we would want to use people’s revealed preference for how they trade those off because those people are the most affected by our decisions and we want to incorporate their preferences. That normative foundation doesn’t really apply to animal welfare where the trade-offs are between people and animals. You may as well use animals revealed preferences for saving humans (ie not at all) and conclude that humans have no worth; it would be nonsensical.
Revealed preference is a good way to get a handle on what people value, but its normative foundation is strongest when the tradeoff is internal to people. Eg when we value lives vs income, we would want to use people’s revealed preference for how they trade those off because those people are the most affected by our decisions and we want to incorporate their preferences. That normative foundation doesn’t really apply to animal welfare where the trade-offs are between people and animals. You may as well use animals revealed preferences for saving humans (ie not at all) and conclude that humans have no worth; it would be nonsensical.