One need only look to times when material resources were less easily won to see the affect of economic sustainability on town planning.
From classical times to the medieval and right up to the urbanisation of the industrial revolution the massing of buildings on the smallest plot of land at the highest density that building techniques could manage was the order of the day.
Not only did this make good economic sense in the reduced amounts of land, materials and labour required, but it made the interactions within society so much more efficient .Incidentally it reduced the surface area of the external envelope where the greatest expense (and the greatest heat loss) lay.
Not until the availability of cheap and convenient personal transport was the massing of buildings revolutionized and Howard's garden suburbs and Frank Lloyd Wright's 'every man his acre' facilitated and towns exploded into myriads of detached houses, isolated from industrial and commercial districts.
The New Urbanism, born in America and Europe in the 1980s has good claim to being the model for sustainable future development – modern tight packed transit towns, self sufficient in food and power, linked by cheap clean rapid transit to one another and to the existing upgraded cities is the way forward.