I have coturnix quail. EASY to raise...except when one of the little turds escapes and you have to chase it through a debris strewn alley!
I like the coturnix because of their egg production. Sure the eggs are small, but they lay almost every day and they are large compared to the size of the quail.
Your biggest cost is going to be housing. Mine are in a converted dog kennel. I got the kennel for free but spent about $100 putting on a roof and netting for the sides, etc...
Their feed is game bird/turkey feed. It MUST be high protein. I and many other quail raisers keep them on unmedicated starter from hatch to dispatch. It is usually 28-30% protein depending on the brand. A 50# bag is around $17.
Attrition rates? Not sure. Haven't lost one yet. I am on year 3 with the original quail I bought. They live 5-7 years. I am getting chicks this month to start training replacements. Chicks are usually between $3 and $5 each.
The only drawback to coturnix quail is they will not hatch out their own young. You have to have an incubator. Very few will attempt to brood. Fewer still will actually be able to hatch out chicks.
You also can NOT raise them in the same run with chickens or ducks. The quail have to have separate housing. There are diseases chickens and ducks are naturally immune to that quail are not. The chickens and ducks can easily infect the quail and you will lose them all.
I also have ducks but put food and water in the quail pen FIRST to keep down the chance of infection. Some people do have quail with chickens, but it is playing with fire as far as I am concerned.
One side benefit of quail is their singing. Their calls, singing and chirps are ADORABLE! Even the crowing of the males is cute. If you have close neighbors, they probably wont notice your birds making noise, or if they do, will just assume it is a wild bird.
If you are in to fly fishing, you have their feathers to use too.
Handy little critters. I hear the meat is good, but haven't eaten any of my quail yet. With this order I have of chicks coming in, I am sure I will end up with extra roos. They have to be easier to kill and clean than the ducks I recently processed.