When I rolled on Nordrassil (first WoW toon) it was pretty much a brand new realm. Disenchanting for profit yielded sick, sick gold to start. I blame (thank?) enchanters who were leveling their profession under the impression that "enchanting is the most expensive profession in the game to level." They'd go out and earn their gold with some other profession and then clean out the enchanting materials on auction (many of which came from me) to level.
Over time, a few too many people caught on to the income potential from disenchanting and they flooded the market and undercut one another into oblivion. In my peak of capitalistic orgasmia, I was pulling in easily 2-300g/day on 60-90 minutes worth of effort. At my realm's low, I was going often over a week with my mats being returned from auction after 24 hours...and they were priced to break even.
Currently, things have stabilized on my realm so that there is still profit to be had, but no more so than with Mining or Herbalism. Cheap greens are in very short supply and not enough people are buying enchanting materials in sufficient quantity to move enough to make it worthwhile.
Currently, I'll D/E whatever I get my hands on and bank it. When my enchanting bags in the bank start getting full, I'll unload a bunch of mats. It usually works out to an extra few hundred gold every month or so, but it's truly effortless and I always keep enough materials on hand to enchant my own gear as I upgrade it.
Get in on the D/Eing while the D/Eing is good, be warned that the market on your realm might bottom out, and be patient. D/Eing is fast, easy gold, but it's not always the road to uber-riches. Some is better than none, however, and I don't regret taking enchanting to 375 in the least.