Apple is also always at least one generation ahead on the process/lithography too because they buy out all of the initial capacity. That alone accounts for a decent chunk of the difference.
I don't think the market is there for fanless non-Mac laptops. Most people would rather have a budget system (no $ for proper passive cooling) or more powerful system.
The low end of the market is for sure bigger but I think Apple has shown that the higher end can be profitable too. Dell, HP, Lenovo, and the other big laptop makers aren't afraid of having a thousand different SKUs. They could add one more for a higher end machine that's fanless.
Most of those SKUs are component swaps. A proper passively cooled laptop would require a completely different chassis design to act as an extension of the heatsink.
I bought a MacBook Air because it was cheaper and met my needs. Being passively cooled was just a nice bonus.
As someone who has been buying Think Pads for the past 20 years, Lenovo needs to spend more time working on thermals anyway. If I don't power my laptop down before stuffing it in my backpack, I'll have a hot, almost dead machine by the time I get to my destination.
I wonder how much of that issue is related to crappy lid open sensors. AFAIK most of them work by sensing a magnet placed in the frame. MacBooks don't do this so your laptop doesn't sleep randomly when a magnet passes over your laptop. It's dumb that they use a single magnet instead of one on each side, but it sure is cheaper.
I think it's 75% Microsoft's fault with modern sleep. They want the machine to go into a low power state rather than sleep so that it can still receive email and other notifications just like a phone does. But since the thermals are total garbage on most PCs, that means even the lower power modes need active cooling which doesn't really work when the machine is in a bag. After a few minutes all the fans are blasting.
I don't think the market is there for fanless non-Mac laptops. Most people would rather have a budget system (no $ for proper passive cooling) or more powerful system.