How far apart? The sources disagree.
There is no universal spacing number for “privacy trees.” Species, mature width, how soon you want the gap closed, pruning and airflow all matter. These are source recommendations, not a planting prescription for your lot.
Simple row and budget estimator
Choose your own on-center spacing after discussing it with the installer. The default 5 ft is R&R’s Green Giant row example; it is not advice for every tree. Cost uses HomeGuide’s $150–$600 per privacy tree range, not mature tree-spade stock.
Sources for the defaults/range: R&R pricing and HomeGuide.