1 vCPU /hr on Cloud Run clocks in at $0.0864/hr compared to $0.0331/hr on VMs with custom CPU or $0.0316/hr for predefined.
1 GB /hr on Cloud Run is $0.009 compared to $0.00094 for Custom RAM or $0.00089 for predefined.
I can assume you can also forget about sustained use discounts.
I would imagine the costs of resources to deliver hot-start performance is significant, but this makes the case for the service a lot weaker, especially for long-running jobs that could just be tossed on a preemptible VM for dramatically cheaper rates.
Sources: - https://cloud.google.com/run/pricing - https://cloud.google.com/compute/pricing
Most use cases could trade startup delay for reduced costs by running GKE with preemtible nodes and Cloud Run on top of it. Otherwise "normal" Cloud Run and Cloud Run on GKE could be combined into a system where on the first request an instance on serverless Cloud Run is started and simultaneously an GKE Cloud Run instance of the same container is ramped up to take over.