Denver Urban Homesteading used to take birds and process them for $20 a bird. They quit doing it. It was on their website, it has been removed now. These people in Berthoud process chickens.http://longshadowfarm.com/There would have to be a minimum number of birds/ animals for on the farm but I bet if the truck was at these various swaps, it would be busy.
I just called them. We have a process date on May 19th. I work at a farm and we have about 85 birds we need to process over the next month or so. I think $4 a bird is cheap. I last year we (the farm I work at) processed birds at a USDA facility in Northern Colorado. We paid $300 for the facility for the day. They aren't doing birds any longer there. Only eggs.