My wife's cousin who just build a massive home right off the 44 in Sapulpa has a huge above ground shelter in her garage. It was built while the rest of the home was being built and has walls that are concrete filled 12" CMU block with approx. 18" poured in place concrete roof. Has venting, storage for supplies, you name it. I can't imagine the additional cost being to much for what you get. My sister in law had an inground shelter put in her garage in Edmond and to me that is just a less fancy tomb. No way in hell would I ever go that route.