Originally Posted by
Eled.
Where did you hear that ?
You can change the RAM without any trouble (same limitations as in any other PC, you need type of RAM your motherboard supports and have to check the maximum), change the hard disk (again, same thing), exchange de DVD player for another disk if it's a MBP (you'd need a case if you want to try that but anyway, it's possible), and some people also manage to change other parts but then it might become a bit trickier (again, I'm talking about their laptops and iMac, MacPro are completely standard nowadays)
MacOS is optimized for the hardware Apple uses, they want it OPTIMIZED, not COMPLETELY CLOSED.
Edit : And NO, just check Crucial buy 8Gb for 45-55€, that's it. There is no way in hell you need to spend 200$ for memory.