You're math checks out; I knew it was something simple but I couldn't remember anything but PV=nRT, and I couldn't remember R's values. I'll accept your properties of water vapor, gas laws almost earned me a D in chem.

But don't the market these things as giving you the ability to seal and freeze a meal, then heat it in boiling water?

*sighs* I guess if the IRS decides to give me some money back, I need to break down and determine this by experiment.