my wife and I live in that general area, make a bit more than they do [tho are a bit older than 30] and have no child expenses whatsoever. Their annual 'spending' is $82k in the first year. I'm not sure if that includes their ginormous mortgage. If it does, wow they are spending only $6,833/mo with 2 kids and a ginormous mortgage. I'd say their spending is WELL controlled. (but what do I know). I cant seem to stay under $10k/month all-in in this area.
edit: it does not include mortgage/property tax: so they're at $11,371/mo spending. Hah! [/condescending glare]. I spend NEARLY $1k/less/mo than them. Although my house is worth the same as their example [give or take 50k], my mortgage + property tax is ~$1200/mo less or so. heh. and there's that no kids thing...