You can forecast and manage costs more effectively by combining knowledge of Kubernetes with a solid understanding of Google Cloud's managed Kubernetes service (GKE). GKE offers several pricing models: pay-as-you-go, committed use discounts, and sustained use discounts. The pay-as-you-go model is the most expensive but provides flexibility in scaling resources. Committed use discounts offer a discount for committing to minimum usage levels, while sustained use discounts provide automated discounts for continuous usage. Spot virtual machines can save up to 91% on costs by bidding on underutilized resources, but require careful strategy and planning to handle interruptions. To optimize GKE costs, it's essential to choose the right VM type and size, check storage transfer limitations, use spot virtual machines, set up groups, take advantage of autoscaling mechanisms like Kubernetes Horizontal Pod Autoscaler (HPA) and Vertical Pod Autoscaler (VPA), ensure that HPA and VPA policies don't clash, consider instance weighted scores, and reduce costs further with a mixed-instance strategy. Automated cost optimization solutions can also help save time and money by providing detailed cost breakdowns and recommendations.