How to use Infracost for Terraform cost estimation?

Question

Accepted Answer

**Infracost** — shows infrastructure cost BEFORE apply (in PR).

**Installation:**
```bash
curl -fsSL https://raw.githubusercontent.com/infracost/infracost/master/scripts/install.sh | sh
infracost auth login
```

**View cost:**
```bash
infracost breakdown --path .
# Output:
# Name                              Monthly Qty  Unit    Monthly Cost
# aws_instance.web
# ├─ Instance usage (on-demand, t3.micro)        730  hours         $8.47
# └─ root_block_device
#    └─ Storage (gp3, 8 GB)                       8  GB            $0.80
#
# TOTAL                                  $9.27
```

**Diff (comparison with main):**
```bash
infracost diff --path .
# Output:
# aws_instance.new (+$12.41/month)
#   + Instance usage (on-demand, t3.large)        730  hours        $12.41
```

**GitHub Actions (posting in PR):**
```yaml
- name: Infracost Cost Estimate
  uses: infracost/actions/setup@v3
  with:
    api-key: ${{ secrets.INFRACOST_API_KEY }}

- name: Run Infracost
  run: infracost diff --path . --format json --out infracost.json

- name: Post comment
  uses: infracost/actions/comment@v3
  with:
    path: infracost.json
    behavior: update
```

**Infracost Registry:** 1000+ prices for AWS, GCP, Azure, Kubernetes resources.

DevOps: How to use Infracost for Terraform cost estimation?