Part of that is that we are reaching the point where a plug-in hybrid is actually more expensive to produce than an EV.

Go to Toyota's website today and you'll see that a Rav4 Plug-in Hybrid is more expensive than the bZ which is the equivalent full EV.

Going to an EREV layout (a series plug-in hybrid where the gas engine cannot drive the wheels mechanically) doesn't really save any costs directly, but allows sharing the platform between EV and EREV models.