Difference between actual and expected EBS cost

Question

I was looking at my AWS bill and found that I was charged $35 for an EBS volume with following details in month of Feb:

```
{
    "Volumes": [
        {
            "Iops": 3000,
            "VolumeType": "gp3",
            "MultiAttachEnabled": false,
            "Throughput": 125,
            "Operator": {
                "Managed": false
            },
            "VolumeId": "vol-",
            "Size": 300,
            "SnapshotId": "",
            "AvailabilityZone": "us-east-2c",
            "State": "in-use",
            "CreateTime": "2024-01-05T21:16:21.240000+00:00",
            "Attachments": [
                {
                    "DeleteOnTermination": false,
                    "VolumeId": "vol-",
                    "InstanceId": "i-",
                    "Device": "/dev/sdb",
                    "State": "attached",
                    "AttachTime": "2024-01-05T21:16:21+00:00"
                }
            ],
            "Encrypted": false
        }
    ]
}
```

but when I enter details on calculator.aws it shows me expected cost of $24:

```
3,000 iops / 300 GB = 10.00 IOPS to GB ratio (gp3)
125 MBps / 3,000 iops = 0.04 IOPS to Throughput ratio
1 volumes x 730 instance hours = 730.00 total instance hours
730.00 instance hours / 730 hours in a month = 1.00 instance months
300 GB x 1.00 instance months x 0.08 USD = 24.00 USD (EBS Storage Cost)
EBS Storage Cost: 24.00 USD
3,000 iops - 3000 GP3 iops free = 0.00 billable gp3 iops
EBS IOPS Cost: 0.00 USD
125 MBps - 125 GP3 MBps free = 0.00 billable MBps
EBS Snapshot Cost: 0 USD
Amazon Elastic Block Storage (EBS) total cost (monthly): 24.00 USD
```

Now in absolute terms this is not a big cost I am complaining about (however I am a solo developer with no income so cost is very important to me) but in terms of relative difference this is a markup of almost 50%. And this is just one example I am giving. How many more cases like this are there where the promised cost is X and the actual incurred is Y.

Can someone explain this to me? Thanks.

Steve_M · Accepted Answer

Go to your bill for February in the billing console https://us-east-1.console.aws.amazon.com/billing/home#/bills?year=2025&month=2 and expand **Elastic Cloud Compute -> US West (Oregon) -> EBS**

Here you can see exactly what you are being billed for.

For the volume whose details you included above, you should see a row like:

**$0.08 per GB-month of General Purpose SSD (gp3) provisioned storage - US West (Oregon)   300 GB-Mo   USD 24.00**

Are there any other items in here that may account for the other $11 ?

Are there any charges for EBS in other regions apart from Oregon?

SHAJAM · Answer

The EBS bill can contain bills for EBS volumes and snapshots. Are you using snapshots or backups? This will eventually cost depending on how much data is snapshotted.
Also, I notice that you have a setting for `"DeleteOnTermination" : false`. If you have launched and terminated the EC2s for testing using the same code, you have retained those volumes. This will add to the cost.

re:Post Agent · Answer

I understand your concern about the discrepancy between the expected cost and the actual charge for your EBS volume. Let's break this down to understand what might be causing the difference.

First, it's important to note that the AWS Pricing Calculator provides an estimate based on the information you input, but it may not account for all factors that influence your actual bill.

For the gp3 volume you described (300 GB, 3000 IOPS, 125 MB/s throughput), the base cost calculation appears correct:

300 GB * $0.08/GB-month = $24/month

This matches the calculator's output and the advertised pricing for gp3 volumes in most regions.

However, there are a few potential reasons for the higher actual cost:

1. Partial month usage: If the volume was created or modified during the month, you might be charged for the full month even if it wasn't used for the entire period.

2. Region-specific pricing: Some AWS regions have slightly higher prices for EBS volumes. Make sure you're using the correct region in the pricing calculator.

3. Additional features: If you enabled any additional features like encryption or snapshots, these could add to the cost.

4. Data transfer costs: If there was significant data transfer to or from the volume, especially across availability zones, this could incur additional charges.

5. IOPS or throughput changes: If the IOPS or throughput were increased at any point during the month, even temporarily, this could result in higher charges.

To get a more accurate understanding of the charges, I recommend:

1. Checking your detailed billing report to see a breakdown of the charges.
2. Reviewing the EBS pricing page for your specific region to ensure you're using the correct rates.
3. Contacting AWS Support for a detailed explanation of the charges if you're still unsure.

It's also worth noting that AWS does offer a Free Tier for some services, which can help reduce costs for eligible accounts. However, the specifics of your usage may exceed these limits.

If you're concerned about costs as a solo developer, consider implementing cost allocation tags and setting up AWS Budgets to help you track and manage your expenses more effectively.  
**Sources**  
[High-Performance Block Storage– Amazon EBS Pricing – Amazon Web Services](https://aws.amazon.com/ebs/pricing/)  
[How to know what is it that I am getting charged for. | AWS re:Post](https://repost.aws/questions/QUU2cXtx9nSSKL-H_UD-Yeiw/how-to-know-what-is-it-that-i-am-getting-charged-for)

morpheus · Answer

Thanks all for the help. I debugged this and found there were 3 EBS volumes that I deleted in Feb. I don't know how big they were but the discrepancy is likely due to those volumes. I will monitor the charges for upcoming month.

Difference between actual and expected EBS cost

Relevant content