I had four. As a rule, by the time the last one arrives, the oldest one is big enough to help out a little. They also help teach and discipline the younger siblings. It doesn't cost any more for a 10-pound bag of potatoes for a family of six or eight than it does for a 10-pound bag of potatoes for a family of three or four, even though it may have to purchased a little more often. Clothes often get handed down, as do toys, bedrooms, etc. The important things in life are often more easily understood in larger families. I am right in the middle of seven, my husband was next-youngest of eight. His parents came from equally large families. My father had nine siblings. Out of all of it, nobody starved, and all got at least an eighth-grade education. Big families are practical and warm, generally.
Already true, and I only have two so far. The 3yo helps the 1yo and they entertain each other as well. When I tell people two is easier than one they think I'm nuts.