Now, of course, how much time one has to spend on WoW in general, and on gold making specifically, varies enormously from person to person. Some people have more free time than others. Some people have other things they want to do with that free time. And you know what? That's perfectly okay.
Yes, time spent is a factor in gold making, but is it as big of one as we may think? "But Tailswish," you may say, "I need more time, no matter what, so I can keep up with those undercutters!" There's certainly some basis for that line of thinking. It's not uncommon to get undercut within minutes, or sometimes even seconds, especially on high population realms.
And here's the biggest thing I've learned over the last couple of years: that's okay. No, really, it is. You don't have to spend all your time trying to stay on top of the people undercutting you. In fact, there's a good chance that trying to do so will hurt your sales.
When I first started out in my gold making journey, I had quite a bit more free time than I do now. More than that, the idea I had stuck in my head was that I had to "use" all of the free time, that doing so would give me a huge advantage. I had everything I crafted sent to one banker, and that banker would run a cancel scan every hour or so.
What was the problem with that? Between running the cancel scan, retrieving everything out of the mailbox, and posting it back up, the whole cycle would often take upwards of a half hour. This means that for the items that continually ended up at the bottom of that huge stack of mail, they were only even on the AH about half the time! It's true that the lowest priced auction sells, but you know what doesn't sell? An item that's not on the AH at all.
There's also another important thing to keep in mind. Supply and demand are constantly fluctuating, and although they'll always go back to equilibrium, there will also be plenty of spans of time when one is greater than the other. Specifically, there will be times, often several in a day, when demand outstrips supply for a given item. At that time, the cheapest auctions get eaten up, and the demand takes a healthy chunk out of the middle.
So what's the moral of the story? There will always be someone there to undercut you. Rarely, if ever, is "camp the AH and run continuous cancel scans" going to be a viable strategy. Instead, be patient. List enough of a variety of items, all at reasonable prices, and simply leave them be. Yes, plenty of them will expire, but that's okay. Plenty of the constant undercutter's auction don't sell, either, but he's paying more and more fees every time he relists, while you're only paying once every 24 or 48 hours. More importantly, you'll be pleasantly surprised at what did sell, and with nowhere near the time investment of the camper.
Gold is valuable, but your time is infinitely more so. Yes, all other things being equal, the person who has 8 hours a day to spend making gold will earn more than the person who has 1 hour, but not nearly as much more as you may think. Now, if you have that massive chunk of free time every day, and want to spend it at the AH, then hey, more power to you. But if you don't, or if you want to say, duck off and play some Borderlands 2 instead, don't think that means you can't make gold. It's about using what time you have effectively, more than anything else.
Personally, I fall much closer to that hour a day end of the spectrum than I used to, and I'm still doing just fine. I can even leave my auctions be for a day or two, and it's far from the end of the world. I don't fear the undercutter, because I see him for what he is, and I know I'll do better than he could ever imagine.