It's not just Apple, any big player can do what you said, but there are connectivity trade-offs in chiplet design. Its been open to any TSMC customer including AMD (which has been doing it well before Apple). Intel has also fabricated its own chiplet CPUs already and is currently sampling them.
> The M2 Ultra has a TDP of 60W. The i9-13900K has a base consumption of 125W, and draws up to 253W under stress.
What of it? RTX 4900 TDP is 600W. Just get a better PSU. It's a desktop computer that is always plugged to the wall, not a laptop on battery. It's irrelevant.
What people care about desktop computer is the performance/price and upgradability/serviceability. That's the math you need to do. In terms of what currently exists in the real world, with Apple, you get a CPU that is weaker than a 13900K or 7950X3D, with a soldered 128GB RAM and a soldered 4TB SSD for about $7000. I can build a stronger computer for less than $1500, and it will be both upgradable and serviceable. But the Apple device isn't going to pay the $5000+ difference with lower electrical bills any time during my lifetime: it will instead become a very expensive e-waste in less than 10 years.