You neglect to mention that with a time preference discount rate high enough, the past counts disproportionately more than the future. As they say, "Tutankhamun was a billion times more important than you".
The Current figure estimated by GiveWell is $3,500 per life saved:
http://www.givewell.org/charities/against-malaria-foundation#Cost_per_life_saved
Wire-heading chickens as an EA cause area
Importance
It is well established that farm animal suffering is one of the largest moral disasters of our time, because of its negative moral value and scale (stemming from low costs).
We see these as an opportunity and call to action. By the same token, we can, with reasonable cost, raise a huge number of chickens who are wire-headed (using electrodes or chicken heroin) to believe they have the most wonderful life imaginable. This positive moral value can far outweigh the positive moral value of flourishing of human lives - a life is a life after all, and heroin is heroin.
Tractability
I mean, they're chickens. We don't foresee them mounting an armed resistance. Besides, if they don't like it, we're doing something wrong.
In contrast to humans who show great resistance to any proposed radical change to their lives (like radical life extension), nobody resists when people put countless chickens through a very contorted experience.
Neglectedness
I mean, are you working on it? Then I guess it's neglected.
Personal fit considerations
We are currently sourcing people have deep insights into the chicken neurology and experience to help lead the UX research front. If you are one of these "bird brained" experts, we need you!
Variations
We must begrudgingly admit that there is a splinter group in our midst which is contemplating instead of raising actual chickens, creating a simulation where even more chickens lead the most wonderful life imaginable. They are currently working on their function applyOptimalHeroinDose(chicken).