Shared costs on GCP are the charges one project runs up for many teams: a shared VPC and its egress in a host project, central Cloud Logging and Monitoring, a shared GKE platform cluster, support, and organization wide services. Left alone they sit in a platform project that no product team owns, so nobody optimizes them and they grow unchecked. Untangling them takes three moves: export billing to BigQuery for the detail the console hides, enforce one label taxonomy so most spend self allocates, and for the genuinely shared remainder pick a defensible split key such as share of compute, share of traffic, or seat count and allocate proportionally. Report the allocated view back to each team every month and the shared layer becomes accountable.
Unallocated shared spend is the spend nobody is incentivized to cut. Here is how the shared layer forms on GCP and how to split it fairly.
Where do shared costs come from on GCP?
The biggest source is the shared VPC. Networking lives in a host project while workloads run in service projects, so network charges and a good share of egress accrue centrally with no obvious owner. Centralized observability is the next source: when every project ships logs and metrics to one Cloud Logging and Monitoring setup, the cost concentrates there even though each team generated its own volume. A shared GKE platform cluster pools many teams onto one set of nodes, so the node bill is one number for many namespaces. Support charges, organization policies, and shared data platforms round it out. None of these are waste by definition, but all of them obscure who is driving the cost.
How do you make most spend allocate itself?
The cheapest allocation is the one you never have to compute, so the first job is a label taxonomy that every resource carries: team, environment, service, and cost center, applied consistently and enforced through organization policy so unlabeled resources are the exception. With labels in place, the large majority of spend attributes itself directly in the billing export, and only the genuinely shared layer is left to split. Export billing to BigQuery rather than relying on the console, because the export carries the label dimensions and the line item detail you need to group spend by team and to see the shared projects clearly.
How do you split the genuinely shared remainder?
For costs that truly serve everyone, choose a split key that matches what drives the cost, document it, and apply it consistently. The table shows defensible keys for the common shared categories.
| Shared category | Defensible split key | Why it is fair |
|---|---|---|
| Shared VPC network and egress | Each service project share of traffic or resources | Allocates by who actually moved the data |
| Central Cloud Logging and Monitoring | Each team share of log and metric volume | Charges back the teams generating the telemetry |
| Shared GKE platform cluster | Namespace share of CPU and memory requests | Splits node cost by reserved capacity, not guesswork |
| Support and organization services | Share of total cloud spend | Scales a broad benefit with each team size |
The rule does not have to be perfect, it has to be defensible and stable. A consistent share of traffic split that every team understands beats a precise method that changes monthly and that nobody trusts. Publish the method alongside the numbers.
A worked example of allocation
A European SaaS company carried a large unowned platform project: shared VPC egress, central logging, and a shared GKE cluster, together a meaningful slice of the GCP bill that no team optimized. We exported billing to BigQuery, enforced a four label taxonomy across the org, then split the platform project by traffic share for network, log volume for observability, and namespace requests for the cluster. Once each team saw its allocated number, two of them cut log verbosity and right sized GKE requests within a month, and the shared layer stopped growing. Figures are verified against billing data and anonymized.
Find your largest project by spend. If it is a host or platform project rather than a product, you have a shared layer that no team owns, and allocating it back is the fastest route to getting it optimized.
Where this fits in the GCP estate
Allocation depends on the same labels and reporting that drive the rest of GCP cost work. Build the taxonomy with labels for cost allocation on GCP, stand up the cross team view in multi project cost reporting, and handle the container specific split in GCP cost allocation for GKE workloads. The full method lives in the GCP cost optimization guide.
Frequently asked questions
What counts as a shared cost on GCP?
How do you allocate shared costs on GCP?
Why does shared VPC make GCP costs hard to read?
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