Given the comments on the RAM and Storage options... we all know Apple deliberately hindered the starting specs specifically to tack on upgrade costs. If you start out at 256 GB of storage, you can sensibly demand $200 to bump it up to 512 GB. Then to double that again it's only another $200. Start out with 512 GB storage and this is actually good enough for most people that they wouldn't need to upgrade, thus Apple loses out on upgrade options that are outrageously expensive for what they are.
Unless/until Apple's 'base' configuration becomes outrageously expensive compared to its competitors, Apple is going to keep its base stats as low as they can get away with.