Cold storage is not cheap storage

Why it works that way

The comparison everyone makes is one number wide. S3 Standard is $0.023 per GB-month in us-east-1 and S3 Glacier Flexible Retrieval is $0.0036, so Glacier is six times cheaper, so move everything to Glacier. That per-GB-month rate is the one thing a colder class always improves, and on most real workloads it is not the number that decides the bill.

A storage class is not a price. It is a bundle of five prices, and choosing a class sets all five at once:

• the storage rate, per GB-month;
• a retrieval fee, per GB read back;
• a request rate, per 1,000 requests, usually higher the colder the class;
• a minimum billable object size, which can be larger than your objects;
• a minimum storage duration, which can be longer than your objects live.

Colder classes trade the first against the other four. That is the design, and AWS states all of it on the S3 pricing page. Only the first one ever makes it onto the slide.

All rates below are us-east-1.

Storage class	Storage / GB-mo	Retrieval / GB	PUT, COPY, POST, LIST / 1,000	GET / 1,000	Min billable size	Min duration
S3 Standard	$0.023	none	$0.005	$0.0004	none	none
S3 Standard-IA	$0.0125	$0.01	$0.01	$0.001	128 KB	30 days
S3 One Zone-IA	$0.01	$0.01	$0.01	$0.001	128 KB	30 days
S3 Glacier Instant Retrieval	$0.004	$0.03	$0.02	$0.01	128 KB	90 days
S3 Glacier Flexible Retrieval	$0.0036	by retrieval tier	$0.03	$0.0004	+40 KB per object	90 days

S3 Standard storage is the first-50-TB rate. Read the table column by column rather than row by row. Standard to Standard-IA cuts storage by 46%, doubles writes, multiplies reads by 2.5, and introduces a retrieval fee where there was none. Standard to Glacier Instant Retrieval cuts storage by 83%, multiplies writes by 4 and reads by 25. Every colder class is cheaper on exactly one line and more expensive on at least three.

Two of the five are not rates at all, and those are the ones that bite. The minimum billable object size means Standard-IA bills 128 KB whatever you actually stored. The minimum storage duration means Standard-IA bills 30 days whatever you actually kept. Neither appears in a per-GB comparison, because neither is a rate. They are floors, and floors only matter when you are underneath them.

Glacier Flexible Retrieval and Glacier Deep Archive swap the size floor for a different mechanism: 40 KB of metadata per archived object, of which 8 KB is billed at S3 Standard rates and 32 KB at the archive rate. No 128 KB minimum, but a per-object tax that a million small objects will find.

Boundaries from the inside out:

1. S3 Standard. Crossing it: $0.00. Free. no floor, no minimum
2. S3 Standard-IA. Crossing it: $0.01 / 1,000. 30-day minimum, 128 KB floor
3. S3 Glacier Instant Retrieval. Crossing it: $0.02 / 1,000. 90-day minimum, 128 KB floor
4. S3 Glacier Flexible Retrieval. Crossing it: $0.03 / 1,000. 90-day minimum, +40 KB per object
5. S3 Glacier Deep Archive. Crossing it: $0.05 / 1,000. 180-day minimum, +40 KB per object

The centre is free. Every ring you cross outward is a toll gate.

What it costs

Getting cold costs a request. S3 Lifecycle transitions are billed per object moved, at rates that climb with coldness: $0.01 per 1,000 into Standard-IA, One Zone-IA or Intelligent-Tiering, $0.02 into Glacier Instant Retrieval, $0.03 into Glacier Flexible Retrieval, $0.05 into Glacier Deep Archive. A million objects into Deep Archive is $50 on the day the rule fires, before a single byte of the cheaper storage has been billed. Ten million is $500.

Getting warm again turns both meters at once. Restoring from Glacier Flexible Retrieval is billed per request and per GB, and you pick the pair:

• Expedited: $0.01 per request and $0.03 per GB. A million objects is $10,000 in requests alone.
• Standard: $0.05 per 1,000 requests and $0.01 per GB.
• Bulk: free on both.

Deep Archive drops Expedited and reprices the bytes: $0.02 per GB Standard, $0.0025 per GB Bulk. Either way, a restore also produces a temporary copy accessible under the same key, billed at S3 Standard storage rates for as many days as you asked to keep it, and you still pay a GET to read that copy.

Exchange between Application, S3 Standard, Glacier Flexible, step by step:

1. Application to S3 Standard: PUT × 1,000,000. Billed on the Units meter, $0.005/1k = $5.00.
2. S3 Standard to Glacier Flexible: Lifecycle transition × 1,000,000. Billed on the Units meter, $0.03/1k = $30.00.
3. Application to Glacier Flexible: RestoreObject × 1,000,000, Standard. Billed on the Units meter, $0.05/1k = $50.00.
4. Glacier Flexible to S3 Standard: Retrieved bytes → temporary copy. Billed on the Bytes meter, 976.6 GiB × $0.01 = $9.77.
5. S3 Standard to Application: GET × 1,000,000. Billed on the Units meter, $0.0004/1k = $0.40. (reply)

Intelligent-Tiering charges for the watching. The monitoring and automation fee is $0.0025 per 1,000 objects per month: $2.50 per million objects per month, whatever they weigh and whether or not anything moves. Objects smaller than 128 KB are exempt: they are not eligible for auto-tiering, are always billed at Frequent Access rates, and are not charged the monitoring fee. Intelligent-Tiering has no retrieval fee and, since 2021, no minimum storage duration for any object. It is the one class here that does not trade the storage rate against the other four; it charges a per-object fee instead.

EBS snapshots price a different shape of the same idea. Snapshots are incremental: only the blocks that changed since the previous snapshot are stored, and you are billed for stored blocks at $0.05 per GB-month. AWS’s own worked example is the clearest statement of what that does to deletions. Snapshot a 10 GiB volume, change 4 GiB, snapshot again: you are billed for 14 GiB. Delete the first snapshot and you are still billed for 10 GiB, because the 6 GiB the second snapshot references is retained and reallocated to it. Deleting a snapshot frees only the blocks that snapshot alone referenced, so deleting the oldest link in a chain usually reclaims almost nothing.

Traps

Early delete bills the remainder, not nothing. A lifecycle rule that moves objects to Glacier Flexible Retrieval and expires them 40 days later pays for 90. The other 50 days are not waived; they arrive as their own usage type, prorated. Standard-IA produces EarlyDelete-SIA at $0.0125 per GB-month, One Zone-IA EarlyDelete-ZIA at $0.01, Glacier Instant Retrieval EarlyDelete-GIR at $0.004, Glacier Flexible Retrieval EarlyDelete-ByteHrs at $0.0036. Overwriting counts as deleting. Transitioning to another class counts as deleting. A tidy-up job that re-sorts objects between classes every month pays the minimum on every class it touches.

Below the floor, colder costs more per real byte. Standard-IA bills at least 128 KB per object, so its cost per object-month is fixed at 128 × $0.0125 below that size while Standard keeps scaling with the real size at $0.023. The two lines cross at about 69.6 KiB. Under that, Standard-IA storage is more expensive than S3 Standard for the same bytes. One Zone-IA crosses at about 55.7 KiB, Glacier Instant Retrieval at about 22.3 KiB. Note also that S3 Lifecycle will not transition objects smaller than 128 KB created after September 2024 unless you add an explicit size filter. AWS made the default the safe one.

Worked comparison. Five million thumbnails averaging 64 KiB, written straight to Standard-IA and deleted after 45 days. Real data: 305.2 GiB. Billed data in Standard-IA at 128 KiB per object: 610.4 GiB.

Line	S3 Standard	S3 Standard-IA
Billed bytes	305.2 GiB	610.4 GiB
Storage, 1.5 months	$10.53	$11.44
PUT requests, 5,000,000	$25.00	$50.00
Total	$35.53	$61.44

The colder class costs 73% more. Of the $25.91 gap, $0.92 is storage and $25.00 is requests, the line everybody compared accounts for four percent of the difference. Add one read per object and Standard-IA takes another $5.00 in GETs plus $3.05 of retrieval, against $2.00 for Standard.

The full round trip of a cheap archive. Take the million 1 MiB objects from the diagram, hold them for the 90-day minimum, then restore everything with Standard retrieval and keep the copies seven days. Transition in, $30.00. Glacier storage for three months, including the 40 KB per-object metadata, $11.40. Restore requests, $50.00. Retrieved bytes, $9.77. The temporary S3 Standard copy, $5.24. GETs, $0.40. Total $106.81. The same three months in S3 Standard with the same single read is $67.78. Glacier costs 58% more, and the storage line it was chosen for is $11.40 of $106.81. Eleven percent of the bill. If the restored data then leaves AWS, data transfer out is charged on top of all of it.

Comparing classes on the per-GB rate alone is the mistake this article exists to stop. The rate you compared is the one the vendor optimised for the comparison. Before you move anything, count the objects, measure the median object size, and write down how long the data actually lives. Those three numbers decide the bill; the per-GB rate is a tiebreaker.