Very few people understand the depth of what you just said.
$2K or even $20K is meaningless for a parent making $100K or more.
Kids have a negative value to a professional class member.
If you engage in agriculture or some similar activity, a child as old as 10 can be a helping hand in some way or the other. No surprises that Amish farmers have a high birth rate.
I think there's just not enough money in the county to induce more babies. The cost would be a shock. Anyone wealthy enough to shoulder the cost would fight so hard against it, it would never stand a chance. IMO the number is probably something like $10k per year per kid. Foster Care pays somewhere between 8k-12k.
It's not clear exactly what the number is, but if one observes individuals who manage to climb out of the low and middle classes and accrue a certain amount of wealth (somewhere in the ballpark of $600k-$1m net worth and up, maybe), pretty consistently not long after that achievement they've settled down and started a family.
I think for many the desire is there, but sufficient de-risking is required for them to be comfortable with acting upon it.