General

Its good if you want to train to 200 really.

much appreciated

Aside from other comments, to give you an actual price, you can probably get away with ~400mil for them. DCO might not be the most effective decent ability out there, but it's still pretty good. Thief boots go for 600mil+ I feel 400 would be fair.

thanks guise

In general, DCO is mainly for slightly increasing effectiveness of your skills, like percentage damage of your skills by small amount, increasing buffs and passives' effectiveness, success rate for Final Attack skills, and benefiting Maple Warrior and Hero's Will.

Rule of the thumb is that if your job has some passive with max level of 5, that's probably going to receive most benefits for the class. i.e: On Mechanic, DCO gives an extra line to the missiles, so it's very very important.

Warriors... I don't think there are classes that will benefit from it immensely like Mechanic does aside from standards. iirc, DA will get 25% Final Damage boost on mastered Advanced Life Sap in a later balance patch, but I'm not sure if that's incremental by skill level, so can't be certain about that.

DCO will give an extra line to DrK's Dark Thrust, since it gains a line for every 15 levels plus 1.

@thesecret: Warriors are the 2nd most popular/expensive class

@petition: Oh truuuuu,
but lets be honest, are those jobs THHHATTT popular?

@thesecret: Lets just ignore the fact that there's more Warrior classes like Kaisers, Zeroes, Heroes, Dark Knight, Aran, Dawn Warriors, Demon Slayers, Hayatos, Demon Avengers, and Mihiles. amirite?

Worth less on warrior shoes because well...Paladin is a warrior
And worth the most on popular jobs, like thieves