[pasbesoin]

In addition to the pure R & D value (with all its uncertainty, but with probable considerable upside in the longer term), doing this likely more than pays for itself in terms of the leverage it provides with/against existing vendors/partners.

This is just my speculation. But, 1) You learn things; 2) You lessen lock-in / dependence, in turn reducing the markup you have to pay on existing production inputs.

Apple's benefited very considerably from the increasing customization and optimization of its phone CPU et al. platform. What's the argument against carrying that over to their computer lines, if and when they can make that a relatively smooth transition?