When we kept pigs (last time was in 2009) we made money on them, but only because of this:
The place I was working at the time had a farm shop anyway - and when we were getting pigs killed, we let customers know, so a lot was presold. We made a LOT of sausages with the poorer cuts that would have taken a while to sell. We froze any unsold down before it went out of date, and we certainly didn't reduce the price for the frozen product.
However, feed was a lot cheaper then, we finished on rolled barley and market veg trimmings (which hadn't been through a kitchen, obviously) which cost us £0.50 for a binful, if I recall (the veg was free).
They seemed to make a useful sideline to an existing business - I don't know if it would have stood as a business on its own.