I'm a high earner and in the instance me and DP parted ways, I would absolutely still expect him to shoulder a good portion of the financial costs of raising our DD. Mortgage free or not.
The way I would see it is, I haven't worked my arse off to provide what I have, for him to then sit and feather his own nest whilst I brunt most of the cost of raising our child.
And if it's gone through the CMS and mediation then i'm going to assume he is paying the minimum he can get away with in relation to his earnings. Whilst still might be a high amount, the CMS amount really is base minimum.
Growing up, my dad used to pay my mum the absolute minimum he could get away with. It was pitiful. My mum gave us everything she could and it was obvious. My other siblings on my dads side now have uni costs paid, deposits put down for them on houses, cars bought on milestone birthdays... funnily enough I also saw him EOW growing up.
The end result is I think my dad is a bit of a wanker and always will. My step-dad on the other hand is a god amongst men in my eyes. When I think back, I remember being taught to swim by SD, him teaching me how to read, saving like a madman to take us on family holidays every year.
The kids do pick up on these things.