The microfilm for each unit is availible from NARA. From my quite limited experience with this, the cost runs about $25-30 per roll, US. However, the number of rolls varies somewhat from unit to unit, depending on length of service, discipline of record-keeping within the unit, and survival of records produced during the War.

Thus, for the 21st Alabama Infantry, mustered in Oct 1861, the records are contained on seven rolls of microfilm. These were purchase by the 21st Alabama Reenactors and donated to the Mobile Public Library Local History branch, where they are availible for everyone to use who is so interested. The records of the 6th Alabama Cavalry, mustered April 1863, and which operated sometimes in detachments scattered over the state, and late in the war, are contained on about two and a half rolls. The 6th Alabama Cav reenactors also purchased these, but elected to retain the microfilm within their membership, undoubtably for their exclusive use.

So the cost for the set of microfilm can vary from $75 to nearly $200, or even more. And you must have access to a microfilm viewer, which most libraries with genealogical holdings will have.