The Two Variables
To determine whether S3-INT is financially beneficial for a given bucket, you need to compare two numbers for every object: what it costs AWS to monitor that object, and what you save when that object moves to a cheaper tier.
Variable 1 — The Monitoring Fee (The Cost):
AWS charges $0.0025 per 1,000 objects per month for the Intelligent-Tiering monitoring service. This works out to $0.0000025 per object per month. This fee is flat — it does not depend on object size. A 1 KB file and a 1 GB file cost exactly the same to monitor.
Critical caveat: objects smaller than 128 KB are exempt from this fee entirely. They are also never moved between tiers. This exemption is a safety valve, not a savings mechanism — those objects simply opt out of the entire tiering system.
Variable 2 — The Tier Spread (The Savings):
When an object moves from the Frequent Access tier to the Infrequent Access (IA) tier, you pay a lower storage rate. Using US East (N. Virginia) pricing as a reference:
| Tier | Price per GB/month |
|---|---|
| S3 Standard (Frequent Access) | ~$0.023 |
| S3 Intelligent-Tiering IA | ~$0.0125 |
| Spread (Savings) | ~$0.0105 |
The savings are proportional to object size. A larger object saves more when it moves tiers. A smaller object saves almost nothing.
The Logic
For S3-INT to be profitable on a per-object basis, the storage savings from moving to IA must exceed the monitoring fee:
$$\text{Savings} > \text{Fee}$$
$$(\text{Size in GB} \times \$0.0105) > \$0.0000025$$
This inequality is the foundation of all S3-INT financial analysis. Every other calculation in this lesson derives from it.
Interviewers frequently ask: "When would you not use S3 Intelligent-Tiering?" The trap answer is "never — it's automatic and free." The correct answer is: "When average object size is below ~250 KB, the per-object monitoring fee exceeds the storage savings from tiering. In those cases, Lifecycle Policies are more cost-effective because they have no per-object monitoring charge."