Purchasing a MB?

I used to make PCs myself, upgrading using the same boxes.
To build a new PC, using an old box
- new MB
- new CPU
- new graphics card
- memory to fit the MB
- HD
- DVD/rw


Here in Japan, the average cost is
- MB: 25,000 yen
- CPU: 25,000 yen
- GC: 20,000 yen
- memory: 12,000 yen for 1 GB
- HD: 13,000 for 360 GB
- DVD/rw: 5,000

So, without the box and other gadgets, the cost is about 100,000 yen.


While for 75,000 yen I get a nice full Dell desktop PC with a 17" monitor...


So, what is the point of purchasing a MB alone, 1/3 of the price of a Dell?!