For the materials and workmanship, yes Kmacs are definitely worth it..
But.. then you're left with the question, Could you do something more fun given $400...
For example, you could buy a gameboy, or 12Tbs or storage, or an HD 7970 gfx card, or a 27" 120hz monitor, or 3.5 BJs at atlantic city, or a 3770 + Cooler, or a compound bow