The cost per keyboard is higher because it is a backlight keyboard.

Replacing a whole palmrest is much harder to do, as you have to completely take the machine apart. Many users and companies won't do this complicated procedures and simply toss units with a defective keyboard. It definitely is not a "fake advantage".

Replaceable Lenovo keyboard is a fake advantage because cost (~90 EUR in EU) is higher than Hewlett Packard aluminium palmrest with keyboard for HP Elitebook and Zbooks. In older Thinkpads cost of replaceable keyboard was ~25 EUR. Assuming that older Thinkpad keyboards were much heavier and stiffer (higher cost of material and NOT made from recycleable plastics) something is wrong here even if we take into consideration higher energy and labour cost in China.

Plastic is not per se worse than other materials. Cheap aluminum, as Lenovo uses on cheap Yoga and ThinkBook laptops, is definitely not a better choice. Those devices do not use the expensive CNC aluminum of more premium designs. They use aluminum as a trick to make it seem like a high quality design when it isn't.

Advantages of plastic:

- Cheaper

- More robust (because it flexes slightly, which means it does not break as quickly)

- Transparent to radio waves (which is very advantageous for a device with LTE)

- Not as heat conductive

The main disadvantage is that plastic feels cheaper, but that is merely perception and does not mean it is actually worse quality. And also, robust plastic designs tend to be thicker, which is also the case here.

To avoid it feeling cheap, Lenovo uses the rubbery-like coating. Plus, this device has an internal metal frame made out of magnesium, so it doesn't flex as much as a pure plastic-construction.

It's  not a cheap plastic, it's carbon/glass fiber reinforced plastic.

I would list it as a big minus point that Lenovo still uses plastic for the case of such an expensive laptop.
Why does Lenovo use better materials for (cheaper) Lenovo Yoga and Lenovo ThinkBook laptops than for this one?
Why isn't there even an option for better materials?