Peace is cheaper than war – however much a court case costs, in both human lives and money, it is better for there to be a trial.  Even if it is more expensive, justice is priceless – it is not something that can be subjected to cost-benefit analyses or bean counting.  The reason why Western countries fund the ICC is not some form of imperialism – simply a desire for global peace, justice and security so they would likely be willing to keep paying much of the cost.