azurerm_ cost estimation
A subscription that routes filtered events from a topic or Azure source to a handler. The subscription is free to define. Cost lives in Event Grid operations and in the downstream handler it invokes.
The azurerm_
Event Grid bills per operation. The first 100,000 operations per month are free, and beyond that operations are about $0.60 per million. An operation is counted for event ingress, each advanced-filter match evaluation, each delivery attempt, and each dead-letter event. Because a single event can generate multiple operations (ingress plus delivery, plus retries on failure), a high-volume source with flaky handlers can multiply operations well past the raw event count. At $0.60 per million the Event Grid line is usually small, but retries against a failing endpoint can inflate it.
The larger cost sits downstream, in whatever the subscription delivers to. If the handler is an Azure Function, you pay Functions execution and, on a Consumption plan, per-million executions and GB-seconds. If it is Event Hubs or Service Bus, you pay that service's throughput and operations. If it is a webhook to a service that egresses data, you pay egress. The subscription is free, but it is a fan-out trigger that starts metered work in another service on every matching event.
The cost-adjacent gotcha is filtering and dead-lettering. Subscribe without subject or advanced filters and every event fans out to your handler, driving both Event Grid delivery operations and downstream execution for events you did not want. And if you enable dead-lettering to a Storage account, failed events accumulate there as billable blob storage plus the operations to write them. Filter tightly at the subscription so you only pay to deliver events the handler actually needs.
c3x flags azurerm_
Terraform example
A minimal but realistic configuration that C3X can estimate.
resource "azurerm_eventgrid_system_topic" "storage" {
name = "blob-events"
resource_group_name = azurerm_resource_group.main.name
location = "eastus"
source_arm_resource_id = azurerm_storage_account.main.id
topic_type = "Microsoft.Storage.StorageAccounts"
}
resource "azurerm_eventgrid_event_subscription" "on_blob_created" {
name = "on-blob-created"
scope = azurerm_storage_account.main.id
included_event_types = ["Microsoft.Storage.BlobCreated"]
subject_filter {
subject_begins_with = "/blobServices/default/containers/uploads/"
}
azure_function_endpoint {
function_id = azurerm_function_app_function.processor.id
}
retry_policy {
max_delivery_attempts = 10
event_time_to_live = 60
}
}Pricing dimensions
What you actually pay for when you provision azurerm_.
| Dimension | Unit | What's being charged |
|---|---|---|
| Event subscription | free | Defining the subscription and its filters carries no per-resource charge. $0 (free) |
| Event Grid operations (free tier) | per month | The first 100,000 operations each month are free across ingress, filtering, delivery, and dead-lettering. $0 for first 100,000 operations |
| Event Grid operations (beyond free) | per million operations | Operations past the free allowance. A single event can produce several operations across ingress and delivery attempts. about $0.60 per million operations |
| Downstream handler | varies | The Function, Event Hub, Service Bus, or webhook the subscription delivers to bills its own execution, throughput, or egress. depends on the handler |
Optimization tips
Common ways to reduce azurerm_ cost without changing the workload.
Filter tightly at the subscription
Use included_
Fix failing handlers to stop retry inflation
Each delivery retry against a failing endpoint counts as another operation. A high max_
Prune the dead-letter destination
Dead-lettered events land in a Storage account as billable blobs and each write is an operation. Set a lifecycle policy on the dead-letter container so failed events do not accumulate storage cost indefinitely.
Batch to Event Hubs for very high volume
For extremely high event rates, delivering to Event Hubs and processing in batches can be cheaper end to end than triggering a per-event Function on a Consumption plan, where per-execution cost dominates.
FAQ
Is an Event Grid subscription free?
Defining it is free, and the first 100,000 Event Grid operations each month are free. Beyond that, operations cost about $0.60 per million. You also pay for whatever the subscription delivers to, such as a Function or Event Hub.
What counts as an Event Grid operation?
Event ingress, advanced-filter evaluations, each delivery attempt, and each dead-letter event all count. Because one event can trigger ingress plus one or more delivery attempts, a single event often maps to several billed operations.
Where does the real cost of a subscription come from?
Usually the downstream handler. The subscription itself is a cheap fan-out trigger, but each delivered event starts metered work in a Function, Event Hub, Service Bus, or external endpoint. Tight filtering keeps that downstream volume down.
Do retries cost money?
Yes. Each retry is another delivery operation. A subscription with a high retry count pointed at a failing handler can multiply Event Grid operations quickly, so it pays to detect and fix delivery failures.
Related resources
More Azure resources
Estimate this resource in your own Terraform
Free, open source, no API key. C3X parses your Terraform and shows line-item cost for every resource, including azurerm_.