By the same logic most Dektops sold are with no dGPUs, so there is no point for AMD/NVIDIA to spend huge amount for R&D to create huge 400-500mm dies (VEGA & GP102).
Except, I can find actual numbers on discrete GPU sales and revenues:
https://www.anandtech.com/show/10864/discrete-desktop-gpu-market-trends-q3-2016/4
Selling about 9 Million Discrete GPUs/quarter on average, and since then mining and gaming hardware sales have been booming, so I expect it is 10 Million+ GPU cards/quarter.
So there is some idea that this is a big enough niche to develop GPU cards for.
You missed the point where you also need a CPU die (AMD or Intel). So you have two dies, one for the CPU and another one for the dGPU.
You missed the point, that you already need to have CPU dies anyway, and that if you create your expensive Super APU, you would still need those normal CPUs anyway, because your Super APU is an expensive niche part, so you still need more normal CPUs for everyone else, and unless you are giving up on the dGPU markets, you still need those as well.
You haven't saved anywhere, you are just creating one hugely expensive extra die for a niche product.
How exactly Lenovo or any other OEM will have lower BOM creating a laptop when they have to buy a CPU from Intel, a dGPU from NVIDIA, 4GB GDDR5 from Samsung, bigger more complex motherboard, bigger and heavier Cooling solution vs a single APU from AMD with 4GB HBM ???
Simple. AMD will be selling it's Super APU for more that the total cost of separate CPU/dGPU/RAM.
Consider also this, such a high performance APU will command higher ASP. Example for desktop,
6-Core CPU = 200 USD
GTX1050Ti 4GB = 150 USD
Total = 350 USD
APU + HBM with same performance as above hardware could be sold at the same or lower price and create higher profits for the manufacturer than the combination of two different dies for CPU + dGPU + PCB + dual coolers etc.
You seem to be forgetting (#1 is key):
1: That it
cost more to build one larger die than two smaller size dies. So your silicon is more expensive, not less. Not only that, but
your product is lower volume niche, while CPU + dGPU are amortized across a wider range of products, so
double whammy on your pricing.
2: That HBM memory costs more than GDDR memory.
3:That Silicon interposer technology is VERY expensive.
You still need a PCB anyway, and few more traces will only add pennies compared to the dollars of silicon interposer.
More expensive silicon, more expensive memory, and more expensive connectivity.
Coolers is nearly a wash. You need one bigger CPU block, vs two smaller ones, but in laptop with that much CPU/GPU power, you likely need dual fans either way. But sure you might save a dollar or two on cooling, but nothing like you cost increase on silicon/HBM/interposer.