Look at the commodity markets for pricing. The trick is to understand what exactly is being priced. Local markets(stockyards where farmers buy and sell livestock) will usually be a little below that so the middleman buyers can make money on the transaction.
If you live near a rural area the local newspaper will usually have a stockyard report indicating the prices of the animals being sold. If you are planning on buying on your own it would be time well spent to spend a good bit of time watching the auctions and getting a feel for the bidding. You need to be careful when bidding though as many livestock auctions have people in the arena who are there to drive the price up on inexperienced buyers. Buying livestock in this manner really requires that you have done the homework and understand the market.
There is a thread around here about a $1200 pig. Check it out.
BTW, cattle and hogs are usually priced by the cwt or hundred weight. So if you see hogs listed at $67 it is for 100 pounds of body weight. Typical market hogs are around 225 to 250 lbs,which makes the purchase price range between $150.75-$167.50. Then you have to arrange for transportation from stockyard to farm or slaughter house.