You're not paying too much more for feed than I am now... For my last two batches I was paying like $11 per 50lbs, but I wasn't happy with the results so I just started feeding them Purina Sunfresh Start and Grow (non-medicated... I wish it wasn't Purina, but it's the only non-medicated anything I can get for them). Here's a big secret- Broiler food and chick starter are pretty much one and the same, except that some companies (some...) put more protein in their broiler food. But 18% is sufficient. Some argue that more protein than that leads to many of the problems broilers are prone to like flip and bad legs, and I tend to agree with them. So if you can find a chick starter that is less than what you're paying per 50lbs (you're paying like $14 now) then you'll save some money. Overall I figured my cost per bird last batch was about $6.50 per chicken. If you're looking for purely cheap chicken you can either feed them only cheap grains and free range, or buy chicken when it's .99 at the store. I raise mine so I can have cheapER humanely raised pastured meat, which otherwise costs more like $15+ per chicken.
Also, if you're looking to save a little more, check out this thread (or parts of it- it's long).
https://www.backyardchickens.com/t/644300/fermenting-feed-for-meat-birds
It's about fermenting the food to increase the nutrition available to the birds. I've been doing it and it really helped my chicks overcome some foot and leg problems. I don't know if it's decreased the amount of food they're eating, but since I'm using 1/2 scratch grains (which are only like $10 per 50lbs) that cuts the cost.
I've heard cornish cross free range fine. I never let mine with the last two batches of cornish cross, but I have some Rosambro now which are really similar and they free range fine (better, in fact, than the red rangers I have housed with them!). This is the first batch of meat chickens I have allowed to free range, and so far so good. My concern before was both their lack of chicken instincts and the fact that I seldom let any chickens who aren't full grown to free range because my dogs leave adult chickens alone but I don't trust them with smaller chickens... and meat chickens aren't really full grown until between 6 and 7 weeks, and by then what's the use of free ranging only the last one or two weeks? This batch I started free ranging at four weeks for at least part of the day every day, and I just keep the dogs inside or tied up when they're out. I figure it's only a short term arrangement, the dogs will live.
Hope that helps!