Here is the deal, child support is an amount determined by both parties income. Then there are certain expenses such as childcare, medical insurance and out of pocket medical expenses that enter the calculation.
Buying things for the child is not child support, its what parents do because they love the children, not because they have to. Child support is money provided to the custodial parent to do as he or she sees fit.
I know that many people do not want to hear this but it's the simple truth, dont shoot the messenger, it's the law.