The performance of the chip will still effect the price though.
The CPU cost for this gen was bargain bin territory, will it be the same next gen? Or will CPU + GPU expenditure be more balanced?
Doesn't quite work that way. Its not like AMD sells them a CPU and a GPU.
AMD shows them what they have, sony/ms tells them what they want. AMD tries to make what they have fit to what they want (design the chip), sony and MS can help with this part, either with money or engineers or both. Once design has been finalized (take this word loosely as this is a moving target based on when they want to release the console) sony and MS contract out the fabrication of the chip.
Sony/MS basically pay some money for AMD to design the chip, and then afterwards pay them royalties for using the chip. AMD doesn't care if its an 8C zen or 16C zen or 40CU GP or 60CU GPU. The royalties you pay pretty much is identical across the board.
Shit gets real though when you go to the foundry, because over there you are paying a certain amount for a wafer. Usable area in the wafers they usually go for is around 70,000mm2. And the process you are going for will determine what you are paying for that wafer. This is also fixed and agreed upon via some sort of contract. So say you are building a 350mm2 chip, you will get around 200 of them from that wafer, if your chip is on a 14nm process it may cost you $15,000 for each wafer, if its on a 7nm process it may cost you $20,000. But even though you have spent $20,000/wafer, not all of those 200 chips are usable (the yield rate is a known thing and factored into contracts) so say they have around 80% yields, then only 160 of those 200 chip are usable. Which will mean the true cost of your chip is (20,000/160) + royalties/usable chip.
Over the course of the generation they could very well be paying AMD the exact same amount as "royalties" for each usable chip or console sold. What changes is the cost at the foundry, as yeilds improve over time or other foundries may come in later offering better contracts. In my loose example, that chip will cost $125 after its left the foundry. If all 160 chips make their way to a console and are sold then sony/ms can b paying AMD as little as $25/console sold as royalties which brings the total cost of the chip to around $150.