They are annoying to raise. After about level 15 you'll find raising STR (the weapon's min/max damage) consumes an excess of 100k per level. However by the time they get expensive they're already by far the most powerful weapon you have.
Get one and spend some time raising it. Even if you just use your ego to finish bosses quickly the effort is worth it.
Mabinogi - Ruairi ch5 - Spliff