All depends on your location and what you can feed.
Chicken is cheapest (~$1/lb here in Seattle Metro area) - but we can't feed that due to allergies
Pork is next at ~$1.50/lb
Beef ~$2.80/lb
Parts (liver, kidney, feet, etc) ~$2/lb
I can get bulk fish (whole sardines) from our buyer's co-op for $1.80/lb (after S&H fees)
Cheapest item ever was "beef rib ends" from the co-op at $0.88/lb - but they're mostly bone and fat with a little bit-o-meat.
If I stick with grocery store pork and beef, I can average right at $2/lb.
When I add in all the extras and exotics I get from the co-op for variety (venison, rabbit, emu, lamb, etc.) I get closer to $2.50/lb average.
I could get the price down if I worked at it - lots of people get free "freezer clean out" specials from ads on craigslist or freecycle. Or if you know a hunter, get their scraps and old stuff.
We did just get a 1/8 cow for us to eat on this year (grass fed, direct from rancher, not cheap, but TASTY) - they threw in the liver, lung, cheeks and tongue for free. 28lbs of "free" stuff!
Denna's down to 1.6% of her expected adult body weight for consumption (~21lbs/week), and even that is too much during weeks when we don't get out and exercise enough. Still... I figure it's about double the cost of feeding a top quality kibble.
But I still think it's worth it.