I just am completing the finish work on a 24 by 26 2 level garage in western wisconsin. there are a number of concrete companies making spancrete like planks in this area. I was about 1 hour from the company that got my bid. It cost 7700 dollars for the planks that were 12 inch thick and 24 long. they were placed on ICF walls and the top coat of concrete over the spancrete was 3 to 7 inches to drain toward the garage entrance. I had the pefect hillside lake lot and have 2 driveways, to maintain for this. To clear and level an area big enough for a one story was not that much more than what i did except the icf walls were costlier. It does stay a constant 50 to 60 degrees year round and I actually have finished the lower garage(it has a window and entry door) as a cabin/bunkhouse arrangement. The garage on top is storeage workshop, etc. I will try to send photos soon.
Ron