Priced from 6 completed Alpharetta homes.
What each construction item costs per heated sq ft. $/sf spreads each item across every included job (a job without it counts as $0), so the column adds up to the construction $/sf used in the estimator. When used is the typical $/sf on jobs that had the item. For your house multiplies the $/sf by the sq ft entered in the estimator.
"Avg. per lot" spreads each item across every included job, counting $0 where a job didn't have it. That column adds up to the soft-cost number used in the estimator. "When used" is the typical bill when the item comes up. "Per sf" converts the per-lot average into $ per heated sq ft for reference; these costs don't grow with house size, so the estimator keeps them as a flat amount.
Change a line's bucket and every average updates. Buckets: Construction scales with sq ft, Soft is a flat per-lot amount, Taxes and Interest have their own lines, and Land, Selling and Excluded stay out of the build averages.