Absolutely. They are most often RPs and have to pick up the slack for any other commitments NRPs make as the law dictates that.
To make it fairer, there should be no reduction in CM for subsequent dependents and costs of the children should be agreed, calculated and split between the parents. So instead of some figure calculated by salary,you look at what that child/group of children costs in terms of rent/mortgage for 2 local accommodations, utilities for 2 homes, uniform/clothes,lunch money,leisure money,hobbies/extra curricular activities, travel to hobbies and school,school trips. 50/50 custody would mean that neither parent would pay the other for the housing/utilities but each would maintain their own. However, travel , clothes, uniform and activities would still be split equally.
There are too many 50/50 dads who actually contribute very little in terms of clothes etc because they have the child purely to reduce CM.
If a parent moves away from the local area/kids to the point it is impractical for them to commute to school, they lose their right to help with housing costs via CM so they'd have to assume the entire rent with no allocated input from the other parent. That would discourage people from moving so far from the co-parent that they cannot benefit from their help with childcare around work/study. Women who move far away from the father to obstruct access or men who move away to start new families and shirk responsibility for existing children.
And yes, as I said earlier, any subsequent children (conceived, step or adopted) will need to be maintained via money outside that allocated for existing children. So no reduction if you have more dependents.