As a divorced father I think he has a financial and emotional responsibility to his kids. Emotional means showing up for all sporting events, helping coach, being involved in the things they are interested in. Helping with homework etc. Having a healthy relationship with your kid.

If he can afford it he should be glad to pay extra for their benefit.

I often had a hard time affording it. My ex didn't complain to much and never brought me to court because she knew I was doing my best and that I wasn't blowing money on TV's or cruises. I was just getting by. I was always fully involved in my daughters life though. Every aspect.