I'm gonna say it probably isn't, unless you plan on doing a lot of farming or are a ring collector. Generally, you won't be able to recover your losses with it quickly enough to justify buying it unless you're a hardcore farmer anyway.
Edit: Or you could just hold on to it until the prices go back up, and then resell it to recover your losses. My point being, though, you're going to find it hard to recover your losses if you just use it for casual farming.
Totally worth to use in DMS because not only does the luck increase your chances of the very desirable shadow orbs and other epic recipe components, it has a minor increase to the dodge and accuracy stats. It's like having r1 knife and adren on a monster which is always a plus.