In my opinion, Hamilton caved quickly, as those contributions' by actors leading to the show's success is questionable at best (unlike say, A Chorus Line). But Hamilton has 8 different audiences per week, and only requires 1 performance for the show. Harry Potter is in a more tenuous position. With only 4 unique audiences weekly, and a two-show time commitment, it's probably making less money than if it wasn't two parts. It's cheaper to see both parts in London, so it isn't quite clear how long audiences are willing to pay the current high prices. Especially once productions become more ubiquitous.
I know New York is expensive, and actors have union dues, agent, and management fees, but $200/week is a 9.8% raise for anyone paid Equity minimum. I am luck when I get a 3% raise at work. And most people don't even get that, if they get one at all. And the kids' parent should be happy with that raise. The two boys are being paid 105K/year and only perform four performances a week each, while the two girls are paid 105K/year and only perform twice a week each.