I think it is a fair assessment, but if antminer s1's were in stock, and you bought one today that number would be in the 500s. The number could be lower if you actually trust calculators (I leave a nice margin of error by giving my self double the power costs, and increasing hardware price slightly.) Those numbers are on a break even 3-4 months point. Then again i'm holding mining funds, until it stabilizes around 700 anyways, granted at this rate that is probably not never