I'm doing pretty much what you describe, but it's only a hobby. I live in a very rural area, and even convincing my customers to pay $2.00/lb for chicken takes a little work. Having said that, I do have a handful of customers who are more than happy to pay it. They LOVE my chicken, and their experience is the best type of advertising.
I've only got one pen for meat chickens (the other is for my layers) which I made out of PVC for a total cost of about $250. At some point, I'd like to put up detailed instructions for this (my redesigned version), since it's so easy to build, and so easy to move. Anyway, you can probably build something cheaper yourself.
Kudo's if you do the processing yourself. As Salatin points out in his book, that's really where the money is at. I'm paying $2.00/chicken right now, and from what I've heard, that's about as cheap as it gets.
I did a break-down of costs and posted it on here:
https://www.backyardchickens.com/forum/viewtopic.php?id=65880 Some of these costs are fixed per bird, and others will go down as the number of birds goes up. Don't count on the pastured birds eating any less just because they are on pasture, however. In fact, my experience has been that they actually eat a bit more as compared to my neighbors' non-pastured chickens.
So, the key to marketing, imho, is to advertise them as "Home Grown" "Pastured" "Grass-fed" or something along those lines. I hope this works out for you, and I hope I haven't said anything discouraging. PPP makes it sound pretty easy, and for the most part, it is! Unfortunately, making a profit is perhaps the most difficult part, but I believe it can certainly be done.