Concrete is more expensive than lumber. A 3,000 sq. ft. stick built structure will be more expensive in 1 story than identical sq. ft. in 2 story. Also, if you can swing the up front costs - full masonry exterior & a Snap Lock¹ metal roof + fiber cement trim is your longest lasting / least maintenance design. Despite the cost, put in a thicker / taller slab (within reason) to prevent flooding (as noted [emoji3595]). Spray foam insulation under the roof (no matter whst product is on top) is very energy efficient however if a leak ever appears, it is near impossible to find the point of origin. ¹Always avoid a Double Lock / Standing Seam panel. ²Even if you are using an "R Panel / Ag Panel" wall, if you *absolutely* have to use an exposed fastener metal roof, put on a properly installed Channel Guard for the roof. But... a Snap Lock panel should be around 5 ~ 7% more in cost, so use Snaps when possible.