There are other animals besides cows and pigs.
Whether or not financial incentive plays a role is a machlokes between the Chasam Sofer and the Pri Chodosh (others as well). As Rav Moshe writes, the minhag in klal Yisroel was always like the Chasam Sofer, and Rav Moshe held that his heter works even according to the Chasam Sofer.