Even in the modern era the cost is still relevant. Bricks are still pretty expensive. If I have 100 acres (square), I need ~2.5 km of wall, at ~150,000 bricks

Even in the modern era the cost is still relevant. Bricks are still pretty expensive. If I have 100 acres (square), I need ~2.5 km of wall, at ~150,000 bricks for a 1m wall single brick-width wall (deter animals, mark property). At the online prices I'm seeing ($0.65), that's ~$100,000. If I have to make it all double width, suddenly its $200,000. $100,000 delta is still pretty relevant for a modern small scale farmer.