They're just ballpark numbers. If a 40 story skyscraper in Tampa saves $40,000 - $70,000 annually ($3,000 - $6,000 monthly), then in order to save $1,200 per month, you'd probably need a large 10 story building. The dollar amounts were just hypothetical. We need to know what they would really be in order to see if any of this is feasible.