Well, we were at 26 sq m per person, but our oldest went off to college so now we're at 32. Moving on up!
Also, I see things like this and I wonder about the people that moan that we have it so much worse off now than in the past. "2 incomes just aren't enough anymore" and the middle class is screwed. People seem to have enough money to buy these bigger houses and eat out more than they cook. Hmm...
On one hand: yeah, absolutely. The standards of living regarding what is considered 'essential' for a middle-class family now vs in the 1950s is a huge change : restaurant dinners, dry cleaning, salon haircuts - or, hell, professional haircuts for ANY children, buying most fruits and vegetables, no preserving, no growing anything, hiring out housecleaning - or buying most household supplies, for that matter, the quantity of clothes deemed 'essential', most gym classes, cell phones and internet, multiple paid-for classes for children under 5, childcare, etc... It's a never-ending stream of expenses that has grown to be 'normal', and, frankly, that can suck up all additional income a family makes (bias statement: you will pry my cell phone and internet out of my cold dead hands, and we do have swimming lessons for out toddler... because we live next to a lake and would like her to know how to float and not drown, and also they're affordable and tax-deductible. For the rest of the list? We're pretty damned close to 1950s levels of spending (or, rather, not-spending).
On the other hand: we looked at the cost difference between building the house we wound up building (technically 1700 square feet according to the plan, but add on an extra 700-ish square feet of finished basement and wow do we have a huge house...) and building a smaller house. Difference for us: an extra 40$/month on our mortgage payment. Difference to the resale value of the house: about 45K, at a conservative estimate from our real estate friend... and this is in addition to the use and value we get out of it while we're living here. (Could we have done without? Sure, but once we have our next kid - hopefully within a year, depending on how quickly I get knocked up - we couldn't successfully work from home wihtout the extra space, and we'd be spending more than 40$/month on commuting expenses, sooo... )
TL;DR: I think the size of houses affects budgets, absolutely. But I think the 'extras' affect budget way more. It's pretty easy (especially for a family) to spend 300-400$/month on restaurants, 200-300 on sports and classes, 100-200$ on clothes (doesn't seem like that much, but it adds up so quickly)... add a few haircuts for the family, maintenance on an extra car, and the 'extra' money spent on not preserving/eating in season/doing one's own household maintenance, and then add daycare expenses on top of that... and there's a full post-tax salary, right there.