Significant difference between Infracost and Azure calculator

[mloskot]

I have a Terraform plan provisioning a new node pool for my AKS:

• VM size: Standard_E2as_v5
• OS: Windows (set via os_type of azurerm_kubernetes_cluster_node_pool)
• VM/Node count: 1
• Premium disk P10
• Pay as go
• Region: UK South

Here is the Infracost estimate calculated based on my Terraform plan:

+ module.aks_windows_node_pool.azurerm_kubernetes_cluster_node_pool.node_pools[3]
  +£84.93
    + Instance usage (pay as you go, Standard_E2as_v5)
      +£68.55
    + os_disk
        + Storage (P10, LRS)
          +£16.38

UPDATE: Suspecting location property of resources in my Terraform code may be not enough, I've added INFRACOST_AZURE_OVERRIDE_REGION=uksouth environment variable and Infracost gives a greater estimate - still lower than Azure calculator's:

+ module.aks_windows_node_pool.azurerm_kubernetes_cluster_node_pool.node_pools[4]
  +£101
    + Instance usage (pay as you go, Standard_E2as_v5)
      +£80.69
    + os_disk 
        + Storage (P10, LRS)
          +£19.82

If I go to https://azure.microsoft.com/en-gb/pricing/calculator/ and request estimate for the same components in the same region, then the total for VM + Disk is roughly twice higher, that the £84.93 above:

What is the reason of such a difference or where am I making the mistake?

[alikhajeh1]

@mloskot I'm sorry I missed this, I answered your other discussion topic but somehow I missed this one. Is #2371 tracking this issue? If not, can you possibly create an issue with the TF code snippet you used to generate that Infracost output? That helps us investigate it quickly as we can reproduce the issue vs guessing what params might have resulted in that output 😅

[mloskot]

@alikhajeh1 The issue #2371 is follow-up tracking my other thread in #2368

However, this thread here may be related to that problem too indeed. So, I'd rather wait until #2371 is fixed, then I test it.
If the estimate discrepancy in comparison to the calculator is still observed, then I will open new issue. Is that OK?

[alikhajeh1]

Thanks - sounds good!

[mloskot]

The new release is out, but it doesn't include a fix for #2371, so I'll keep this thread open.

[mloskot]

For the archive records, fix is available and it works, see #2371 (comment)
Thanks

[aliscott]

Thanks for confirming @mloskot 🙏