Storage costs the same on every new iPhone Apple sells. Moving from 256GB to 512GB is $200 on iPhone 18 Pro, on iPhone 18 Pro Max, on iPhone Air and on iPhone Duo, the step to 1TB is $400 on all of them, and the step to 2TB is $600 wherever it is offered.
That makes capacity a flat fee rather than a percentage, and it has one consequence Apple never spells out: the same $200 is a fifth of a cheaper iPhone’s price and a tenth of the foldable’s.
Every capacity Apple prices on its new iPhones
| Model | 256GB | 512GB | 1TB | 2TB |
|---|---|---|---|---|
| iPhone 18 Pro | $1,199 | $1,399 | $1,799 | $2,399 |
| iPhone 18 Pro Max | $1,299 | $1,499 | $1,899 | $2,499 |
| iPhone Duo | $1,999 | $2,199 | $2,599 | $3,199 |
| iPhone Air | $1,099 | $1,299 | $1,699 | Not offered |
| iPhone 17 | $929 | $1,129 | Not offered | Not offered |
Those are Apple Store figures. The iPhone 17 numbers are its unlocked prices, and Apple advertises it from $899 with a connectivity discount applied. The iPhone 18 Pro prices also assume activation with AT&T, T-Mobile or Verizon at checkout.
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A flat fee hits a cheaper iPhone harder
| Model | Step to 512GB | Step to 1TB | Step to 2TB | 512GB step as a share of the base price |
|---|---|---|---|---|
| iPhone 17 | $200 | Not offered | Not offered | 22 percent |
| iPhone Air | $200 | $400 | Not offered | 18 percent |
| iPhone 18 Pro | $200 | $400 | $600 | 17 percent |
| iPhone 18 Pro Max | $200 | $400 | $600 | 15 percent |
| iPhone Duo | $200 | $400 | $600 | 10 percent |
The shares in that last column are ours, not Apple’s. They say that a buyer stretching to a $929 iPhone 17 pays the largest relative premium for doubling capacity, and a buyer already spending $1,999 on a foldable iPhone Duo pays the smallest.
Climbing the whole ladder tells the same story. On iPhone 18 Pro, going from 256GB to 2TB adds $1,200, which is almost exactly the price of the phone again. On iPhone Duo the same $1,200 is 60 percent of the base price.
The carrier discount does not change the ladder
Apple’s headline iPhone 18 Pro prices require picking a US carrier at checkout, and the unlocked price is $100 higher. Because that $100 applies at all four capacities, the steps stay at $200, $400 and $600 whichever route you take.
Apple never states the delta as a number anywhere on its pages. It states only that connectivity discounts are reflected in the advertised price for customers who connect with select carriers at the time of purchase.
What it means when you are choosing between two iPhones
Because the steps are identical, the gap between two models never widens with capacity. iPhone Air is $100 below iPhone 18 Pro at 256GB, at 512GB and at 1TB, and iPhone 18 Pro Max is $100 above the smaller Pro at every tier, as our Pro and Pro Max comparison shows.
So the two decisions come apart cleanly. Pick the phone you want on its camera, battery and chip, then pick the capacity, and neither answer changes the price of the other.
What Apple has not said
- Why storage is priced as a flat fee across four very differently priced iPhones. Apple gives no explanation on any page.
- The $100 gap between its carrier-connected and unlocked iPhone 18 Pro prices, which appears only as the difference between two numbers.
- The full capacity ladder and prices for iPhone 17e, which Apple lists from $699 at 256GB, and the higher tiers of iPhone 16, which starts at 128GB for $829.
- Usable capacity on any model once iOS 27 is preinstalled, so no tier’s real free space is published.
iPhone 18 Pro and Pro Max pre-orders open at 5 a.m. PT on Saturday, September 12, ahead of availability on Friday, September 18. iPhone Duo pre-orders follow on Friday, October 16, at the same $200, $400 and $600 steps.
