It looks like Apple is pricing their devices according to the manufacturing cost at the time of release and their margin target. As prices of semiconductor went on a nose dive in all areas (processors, volatile memory, non-volatile memory) in the past year, Apple is able to increase their margins on the iPhone by keeping prices the same. Their upgrades are also huge margin makers. So by taking away the lower storage option they increase margin. (Recall 128GB of extra flash is like $4 on market, which now they force you to buy at $100) It's a win-win I guess because people don't think of it as an increase.
Still surprising that they didn't increase the price of the non-Max Pro to create differentiation (or in other words cut the 128GB Pro and make 256GB the default at $1099). They can definitely afford to do it at minimal loss to their user base. With the volume the iPhone is shipping in, Apple really does not need to be concern with its market share. On the other hand, Apple is more worried about the Mac sales. As you can see in the aggressive pricing of the Mini and the MacBook this year compared to last year. (I think the coming MBA will get a price cut from the M2)