Shorthorn,
You are Backgrounding. The ration tends to be less energyfor this. In our area, the cost (including yardage) tends to be in the mid $40/cwt range. In Roseburg Oregon, they charge on the gain, up to $38/cwt I hear. This is very viable to winter calves. The key to backgrounding is there's lots of low cost feeds that will work when you are framing them vs fattening them.
Things change when calves are fed the last 90 days. Costs hit around $50.00 cwt. This is reflective of a higher proportion of grain. I think our finish costs tend to be lower because we have a lot of food processing wastes,
PPRM