I know from first hand experience having 50/50 shared with joint custody. Mine was not exactly 50/50. Besides, the child support in my situation was nothing to throw up arms about. I was responsible for healthcare. His income was say $60,000 per year and mine $35,000. He was obligated for $300 a month for three kids. Really nothing to throw a fit over. I just had it direct deposited into a savings account, so it could be used for a car or college for the 3 kids.
It is calculated based off of the income of both parties. The courts take the approach that the children should not suffer financially because the parents are incompatible. Thus, with the parent having the latter part of the total income percentage, receives support to help sustain the way of life that the children could have had if the parents were together. As stated earlier, it does not account for separate living expenses.
mom2gr8kids, I would ask the judge to average out the last...say 3 years of your income. Since you just started this new job that pays double. It is not what was "historically relied upon by the parties prior to the dissolution of the relationship" - per the Kansas Child Support Guidelines. It is not unreasonable for you to ask this.
My ex had started a new job that nearly paid double what he was making prior....well he was unemployed for 9 months with no income. The judge allowed to average the income for the last 3 years...which was in the ex's favor with 9 months of 1 of those years with no income. Granted, any time there is a "change of circumstance" a motion can filed.