Launching 60,000,000,000 Chickens: A Give Well-Style CEA Spreadsheet for Animal Welfare
The meat industry breeds horrors on an unprecedented scale. History has never before witnessed suffering at this scale, nor seen it inflicted so carelessly and senselessly.
In 2013 alone, we slaughtered 60 billion chickens.
By comparison, the worst human tragedies cap out at around 145 million by even the most pessimistic estimates. If it’s difficult to conceive of numbers this large, think of it this way: you could murder 145 million human beings very year for the rest of your life and still not get to the chicken death toll for a single year. In fact, only around 100 billion humans have ever existed.
We can’t even blame any of this on our historical savagery. With all our sci-fi technology and economic progress, we are still choosing to commit these atrocities. In fact, it is precisely those advances that allow factory farming to function at this unfathomably grotesque industrial-scale.
Now perhaps you could argue from the standpoint of speciest solipsism. Whatever the cortical neuron counts say, we don’t really know what happens inside the brain of a chicken. Do they suffer? Are they even really conscious?
It suffices to say–as a general moral principle–if there is reasonable doubt as to whether or not a creature suffers, you should probably not kill 60 billion of them every year.
At this point, any reasonable person would just stop eating meat. But I’m not reasonable, just rationalist. So okay, let’s do the moral calculus.
Here’s the math on moral/financial fungibility:
For 1000 calories of meat, chicken produces 2kg CO2-equivalent, versus 10kg CO2-equivalent for cows
CO2 offsets cost around $10/tonne, or $0.01/kg.
Both species provide ~260g protein and ~2500 calories per kg of meat
Per life, chicken produces around 1.9kg of meat, versus 212kg for cows
Due to elasticity, reducing consumption by 1kg only reduces production by ~0.7kg for both chickens and cows
If you’re not eating meat, you have to replace the protein and calories. At baseline, flour is 4,464 calories/dollar and 134g protein/dollar.
Since we’re talking about financially offsetting meat consumption, this analysis does not rely on estimating the relative moral patienthood of chickens versus cows, or their relative living conditions. 
Perhaps the most important number is the cost to prevent an animal from being farmed. Initial estimates were as low as $0.10/life, but later came under scrutiny. One estimate puts the cost at $5.70 to save a chicken life, with pigs being around $150. Since that implies costs scales about linearly with meat-produced, I’m assuming $636 to save a cow’s life, but these numbers are all speculative. Note also that these are estimates for one particular intervention.
From these conversions, we can calculate the “true” financial cost for each animal. Chicken comes out to $3.42/kcal versus $4.18/kcal for beef. Anchoring on protein yields similar results: $2.76/100g for chicken and $3.48/100g for beef. 
Finally, what about plant-based meat alternatives? As Kelsey Piper writes:
plant-based products are already difficult to distinguish from the originals, while having a lighter carbon footprint and no impact on animals. If you avoid beef by switching to plant-based meat products, you really are improving the world and improving conditions for the humans and animals that live on it.
The problem is still cost. Beyond Beef is $6.74/lb or $14.83/kg on Amazon (cross-check), versus just $8.80/kg for cow beef, or $10.93 for suffering and carbon offset cow beef. In other words, for the price of 1kg Beyond Beef, you could get a kg of cow beef, and use the remaining money to offset 6kg worth of meat. 
So it’s not cost-effective short-term. In the long run, maybe there are benefits to demonstrating demand for plant-based meat alternatives, but that’s hard to quantify and I’m skeptical. You’re probably better off eating cow beef and donating the $6.03/kg to the Good Food Institute which accelerates the development of plant-based proteins.
 If you’re curious anyway:
Chickens are treated much worse than cows. Brian Tomasik estimates as 3x multiple.
 As Scott points out, normal reasoning starts to break down here. If you really can offset 1kg of CO2 for just $0.01, the lesson isn’t that you can eat all the chicken you want. The lesson is that you should pour all your money into CO2 offsets!
Alternatively, rather than asking “how much does it cost to eat ethically neutral chicken”, you should just ask “how can I do the most good with my money?” Stated otherwise, I don’t really get the Supererogatory approach to ethics, and see failing to do good as similar to causing harm.
In that worldview, the real cost of 1kg chicken meat isn’t $8.55, it’s the 4 mosquito nets you could purchase for that same amount, with $0.55 leftover to eat rice and beans.
 Beyond Beef has its own carbon footprint. They claim to emit 90% less GHG than cow beef, which makes the offset negligible.