Apple's strategy is clear: charging $1,149 for 256 GB and justifying it as a huge jump from 64 GB, while in reality the majority of iPhone users wouldn't need any more than 128 GB at $1,049.I do not see why adding the 128GB tier in between 64 and 256 would mean 256GB and 512GB would have to be more expensive.
64GB: US$999
128GB: US$1049
256GB: US$1149
512GB: US$1349
They are the prices we are likely to get, just with the 128GB version not existing. A set price per GB for multi-tier upgrades is consistent with other products, like the 2018 MBP.
Of course, these prices are still hard to swallow.
64GB: US$999
256GB: US$1099
512GB: US$1229
or even lower would make the up-sell a lot easier to swallow, and may end up recouping the lost revenue in costs in extra purchases of higher tier models.
I really wish Apple would stop price-gouging on storage. 128 GB SSDs in MacBook Pros, 5400 RPM HDDs in iMacs, etc. But as long as the strategy keeps working, Apple will keep prioritizing profit over the user-experience of base-model products.