Our mixed flock of 20 hens go through a 50# bag of feed in about 10 days. That works out about the same as Angela's rhodies. They get lots of other goodies to eat too (scratch wheat, coconuts, yard trimmings, fresh grass, kitchen scraps) and are often let out of their large fenced yard for a few hours in the early evening.
We're currently getting about 70-80% egg production each day. Most of our hens are a little over a year old, and the 4 buffies are closer to 1-1/2 years old. They'll lay fewer eggs as they age. That's normal.
You can expect similar percentages with fewer hens. You also have to factor in the cost of housing, unless you let them run wild, in which case you'll get fewer eggs and have a higher mortality rate due to predators.
We keep only hens because they're far less noisy than the roosters, but that does mean that we don't get new chicks from our girls, so when they go broody they're just taking up space (& eating feed!) until they snap out of it. (They don't lay when they're broody.)
But above all, we keep chickens because it's fun! We love our flock and the fresh eggs we get from them. :-)
You can learn a lot more about chickens at our island chicken group here:
http://groups.yahoo.com/group/hawaiichickens/
aloha, Liz
"The best things in life aren't things."