If the utility of two people being vegetarian for a year is roughly twice that of one person being vegetarian for a year, and so on, then if they’re contributing money to make more vegetarians, then they’ll probably want to give a lot more than the cost of one vegetarian. In practice, the marginal value of a vegetarian year changes very slowly as the number of vegetarians increases, so if a consequentialist altruist is buying vegetarians at all, they’re probably buying them in bulk.
Someone who did this might also become vegetarian or vegan themselves because it was useful for personally convincing others to do the same, or in order to feel more consistent. It would also be worth it for them to change their diet in addition to contributing money if their productivity, etc. didn’t decrease by more than the cost of making another person vegetarian.
Their own quality of life would not be a significant factor in itself (though its effects on how much they accomplish would be), unless they value their own wellbeing more highly than that of others, or are more adversely affected by the diet than the typical person is (for example, it’s more difficult to be vegetarian if one also needs to eat a low-starch diet for health reasons). If they’re paying to encourage others to become vegetarians, and also believe that being vegetarian decreases the typical person’s quality of life, then they must value the reduction in animal suffering more than the benefits the other person would get from eating animal products.
If the utility of two people being vegetarian for a year is roughly twice that of one person being vegetarian for a year, and so on, then if they’re contributing money to make more vegetarians, then they’ll probably want to give a lot more than the cost of one vegetarian. In practice, the marginal value of a vegetarian year changes very slowly as the number of vegetarians increases, so if a consequentialist altruist is buying vegetarians at all, they’re probably buying them in bulk.
Someone who did this might also become vegetarian or vegan themselves because it was useful for personally convincing others to do the same, or in order to feel more consistent. It would also be worth it for them to change their diet in addition to contributing money if their productivity, etc. didn’t decrease by more than the cost of making another person vegetarian.
Their own quality of life would not be a significant factor in itself (though its effects on how much they accomplish would be), unless they value their own wellbeing more highly than that of others, or are more adversely affected by the diet than the typical person is (for example, it’s more difficult to be vegetarian if one also needs to eat a low-starch diet for health reasons). If they’re paying to encourage others to become vegetarians, and also believe that being vegetarian decreases the typical person’s quality of life, then they must value the reduction in animal suffering more than the benefits the other person would get from eating animal products.