3.1 Factors That Affect Azure Costs

Quick Answer: Azure bills on a consumption-based (pay-as-you-go) model. Your cost depends on which resource (resource type), how much you run it (usage), where you run it (region), how much data leaves Azure (outbound bandwidth), your subscription type, and any third-party Marketplace charges. The big savings levers are Reserved Instances, Savings Plans, Azure Hybrid Benefit, Spot VMs, and right-sizing.

The Six Primary Cost Factors

AZ-900 phrases these questions as "Which factor affects cost?" or "What can reduce cost?" Memorize the six drivers below — they appear verbatim in Microsoft's exam objectives.

1. Resource Type

Each service has its own meter and unit of measure. A meter is the thing Azure counts; the rate per meter is set per region.

2. Usage / Consumption

You pay for what you consume: compute is metered per-second (rounded), storage per GB-month, transactions per operation, and egress per GB. Stopping (deallocating) a VM stops compute charges, but you still pay for the attached disks.

3. Region

The identical VM costs different amounts in different regions because of local electricity, real estate, currency, demand, and regulatory factors. Example: a standard D2s v5 VM is typically cheaper in West US 2 than in Japan East or Brazil South. Choosing a region is therefore both a latency/compliance decision and a cost decision.

4. Bandwidth (Data Transfer)

Trap: Candidates assume "data transfer is free." Only inbound is free. Egress and cross-region replication carry charges — a key reason geo-redundant designs cost more.

5. Subscription Type

• Pay-as-you-go — standard rates, no commitment.
• Enterprise Agreement (EA) — negotiated volume pricing for large organizations.
• Cloud Solution Provider (CSP) — a Microsoft partner manages and bills the subscription.
• Free Account — 12 months of popular free services + a USD 200 credit usable for 30 days + always-free services.
• Visual Studio subscribers — eligible for discounted Dev/Test pricing (no Windows license charge on VMs).

6. Azure Marketplace

Third-party (non-Microsoft) software and managed services purchased through the Marketplace bill on top of your Azure usage and may have separate licensing terms. A firewall appliance or a managed database from a partner appears as a distinct line item and is not covered by your Microsoft volume agreement, so it is easy to overlook when forecasting spend.

CapEx vs OpEx Framing

AZ-900 connects cost factors to the capital expenditure (CapEx) versus operational expenditure (OpEx) distinction. On-premises servers are CapEx: a large up-front purchase that depreciates. Azure consumption is OpEx: a variable, ongoing bill with no up-front asset. Reservations are a hybrid — you commit to OpEx in advance to capture a discount, but you do not buy hardware. Understanding which strategy shifts spend from CapEx to OpEx (and why finance teams favor OpEx for agility) is a recurring exam theme.

Cost-Optimization Strategies

Azure Hybrid Benefit

Reuse existing Windows Server or SQL Server licenses covered by Software Assurance instead of paying for them again in Azure.

Reservations, Savings Plans, and Spot

Right-Sizing and Auto-Shutdown

A dev VM running only 8 business hours per day costs roughly one-third of a 24/7 VM — about 67% savings. Auto-shutdown is built into the VM blade in the portal. Azure Advisor surfaces underutilized VMs, idle disks, and orphaned public IPs for deletion.

Choosing the Right Lever (Worked Scenario)

Suppose a team runs a steady production web tier 24/7 and a separate analytics cluster that only runs interruptible nightly jobs. The optimal mix is: a 3-year Reservation or Savings Plan for the always-on production tier (predictable, deepest committed discount), and Spot VMs for the analytics cluster (interruptible, up to 90% off). If those production VMs run Windows Server with Software Assurance, layer Azure Hybrid Benefit on top of the reservation to remove the OS license charge. Finally, set auto-shutdown on every developer's personal test VM.

This single design touches four of the five optimization levers and is exactly the kind of multi-part scenario AZ-900 builds questions around.

Storage Tiering as a Cost Lever

Blob storage tiers also drive cost. Move data you access daily to Hot, monthly data to Cool, rarely touched data to Cold, and long-term retention to Archive, which is the cheapest per GB but charges a rehydration delay and fee to read. Matching the access pattern to the tier is a no-downtime way to cut storage spend.

On the Exam: Distinguish the three commitment models: Reservations (best for fixed size/region), Savings Plans (flexible across families), Spot (deepest discount, evictable). Hybrid Benefit always requires existing licenses with Software Assurance — it is not a discount you simply turn on.