Here is information about what happens to the animal you paid to have sacrificed during hajj. If there are 30 people or more, one of their party actually go to the slaughterhouse on behalf of the group . On that same site, you can find why each animal is priced the way it is:
The price per head of sheep includes the cost of the animal and the contribution of the pilgrim towards the cost of Shari’ah and veterinary-related services, as well as the cost of slaughtering, skinning, cleaning and transportation of meat for distribution to the eligible poor.
