[nhumrich]

The price. You seem to be comparing MacBooks to cheaper laptops. "High end" laptops such as Lenovo X1 Carbon, are slimmer, and lighter than MacBooks. Another reason however is thermal distribution. A MacBook shell acts as a heat sync, but a plastic shell does not. So MacBooks don't need as much airflow.

[GekkePrutser]

Carbon fibre's lower heat conductivity can be a good thing too though. Less heat leaking through to the keyboard deck where it could bother the user.

[donboscow]

So, using aluminium as body material is one of the factors why Macbooks are so slim? Why can't the bulkier laptops use the same? Price?

[tony-allan]

A higher price allows the use of particular materials, precision engineering, and slim custom components.

Some is a huge R&D spend, the bill of materials, and assembly techniques.

[donboscow]

Yeah, I get the R&D part, what I want to know, what specific improvement here does the R&D here contribute to?

[coldtea]

"the use of particular materials, precision engineering, and slim custom components"

All of the above require R&D. Techniques for unibody construction for example required a lot of R&D in machining parts, precision opening of ports, and so on.

[kingkongjaffa]

The hard part is also not doing it once really well, it's doing it 100's of millions of times also really well.

[maximus-decimus]

Interesting video about how the only reason you even need a fan in the mac book pro is because how hot the shell of a laptop is allowed to get is legislated so you don't burn yourself on it.

https://www.youtube.com/watch?v=ghDvyItIHTY