Prices vary from place to place, but as a guide -
Sempron 2200+ = 2.5k
C18G-400 mobo = 4.0k
256MB DDR400 = 2.2k
Seagate 80GB = 2.8k
Liteon CD-drive = 0.7k
Sony FDD = 0.3k
Cabinet + PSU = 1.0k
Total = 13.5k
This is slightly over your friend's budget, but it will be worth it if he can manage it. He'll be able to play most games on it. If he must, he can keep within 12k by omittimg the floppy drive, use 128MB RAM instead of 256MB, 40GB HDD instead of 80GB.