That definitely seems expensive! As for how people afford it: for us, we did different things for each kid.
#1 - we paid $350 a month for half-day Montessori when she was 3, then we kept her home when she was 4 (and homeschooled for Kindergarten.
#2 - he didn't attend school until he was 4, and it was through a lottery that we got a pre-k spot for free, half-days, and only from Aug- Dec as we moved out of state at that point.
#3 - He also didn't attend until age 4, and...