The cost of raising a pig is variable. Yes, I know that answer will drive you crazy, but it's the truth. This article can be viewed as the cliff notes on the cost of buying, feeding, and processing pigs from weanling to slaughter.
The cheapest pigs to buy are commercial weanlings. A weanling pig is approximately 8 weeks and is eating solid feed. The average price to break even on a weanling pig is $46.43.
A pasture-raised pig will cost less to feed per day but may cost more to feed per pound of meat produced. A pasture-raised pig will move around more than a pig housed in small pens i.e., these pigs burn more calories per day than penned pigs.
Most pigs are slaughtered at a live weight of 250lbs to 300lbs. Once slaughtered and dried, the carcass will weigh on average 30% less than the live weight. A 250lbs pig will produce a hanging carcass of 175lbs.