Good questions. We may not value the life of other species as much as the life of humans, but what would be our answer if God asked us how we have treated His creation?
Use of other species as food is a norm in nature, humans are not an exception in this respect. Our body indicates omnivorous feeding habits. Rather than asking is there a rational case for using animal products, maybe we should ask is there a rational case for not using animal products?
Protecting animal populations from extinction and reducing the damaging effects of growing human populations on this planet are two reasons to reduce the use of animal products. Reducing the use of meat may also have positive health effects. Otherwise, I do not see much reasons to ban the use of ethically produced animal products.
Cost-benefit analyses are an ethical tool that can be used to justify the use of animals. The results of cost-benefit analyses depend on what value we give to animals (is the life and suffering of other species equal to that of humans?) and what consequences are included in the analyses (do we include indirect long-term effects on future generations?). These tools are used in animal experimentation but I assume that conscious use of this type of ethical tools is very rare in everyday life. Just business-as-usual without too much thinking.