One thing I don't understand from the documentation: with old fashioned AppEngine web apps, I can enable billing, set a maximum spend of $1 per day, and be good for low traffic sites, with a very low (or zero) monthly cost.<p>I think that for flexible platform apps, you are always paying for a continuously on micro or small instance so the cost per month of a low traffic Ruby app might be $5 to $10 per month. Is this correct?