I don't have any real solid numbers as to cost but I did some research before getting my last batch of broilers. These are estimates on 100 birds, I ended up losing half my birds to some domestic mink that moved in two weeks before butcher time.
Assuming you don't have major losses to predators, disease, freezing...anything, you should be able to get them raised and butchered for about $5 each, not including your time, housing, electricity, transport to processor.
Here's how I figure (going with 100 here because it's easier with the even numbers)
100 chicks- $77 (from Central Hatchery which I can recommend with confidence)
1400 pounds of feed- $240- possibly less if you can get it in bulk
Processing- $180 (This is what it costs at our local processor, I consider it a steal)
Total comes just under 500 for the 100 birds.
A couple other notes- the amount they eat will increase dramatically each week. The first week a 50# bag might last the whole week. By the last week you're at about a bag a day.
My birds were free range- I'm not sure how that affects feed consumption but I'm thinking they eat more because they burn off more than the free feed they get while they're ranging. They taste much better though.
My chicks were cornish cross from central hatchery in NE. I couldn't be happier. They were very active, often spread out all over their paddock. They were even a bit of a challenge to catch at butcher time- not usually a problem with broilers. The one critique I have is that they didn't finish as uniformly as other batches I've raised. Some were quite small while others were butterballs. They were straight run but there was even more of a difference even between pullets and cocks than usual. I don't have any weight measurements yet (they come back from the butcher tomorrow) but I would guess they will dress between 2.5-4.5 pounds.