2 part shop/garage question.

[HeloCrewChief]

Hey guys. I hate being the guy asking "how much" but, I have been getting quotes all over the place on having a garage built behind my house. I don't really know any contractors so, I'm hoping someone can give me a rough estimate of what seems fair. I'm looking to build an oversize 2 car or 3 car garage. Very basic garage with electrical, no plumbing and roll up garage doors. I will also need the concrete slab laid down with a small driveway in front. I've gotten quotes from $15,000-$35,000 so you can see why I'm a bit confused on why there is such a price difference between contractors. I've attached a couple of pictures of the two styles I'm contemplating. I live on a 12,000 square foot lot so, I don't have too much room to play with and the only access to the back is an RV style access. Also, I'm in Washington State so, If anyone can recommend someone please let me know.