I play the AH too, and I'm with some of the other people that replied; I hate farming. I don't really even like crafting to make money. But playing the AH has become almost like a mini-game to me ever since I started playing WoW and figured out how to use Auctioneer. In fact, the reason I was looking around in this forum section was because I was going to ask a general question about how "liquid" most of you high-rollers are.
But anyway, yeah...farming and crafting can make you some really great money, but so can playing the AH. It just depends on how much time and effort you want to invest, and what gives you the most enjoyment. Playing the AH (only buying and selling, that is) is definitely an art. Auctioneer is a great tool, but it's not a magic addon that prints money for you. You really have to spend a lot of time learning the market, memorizing trends and items, getting to the point where you can scan lists of auctions and know within an instant whether or not something is worthwhile.
There was a period of like six months when I wasn't really playing WoW, but for some stupid reason, I left my account active. Even though I wasn't playing, I would still log in every other day and do some AH work for 30 minutes or so. I think that's when it really started to become that "mini-game" mentality; like a game within a game, seeing how much gold I could make by doing nothing except except sitting in the AH and checking my mail. It kinda sucks now, because old habits die hard, and my AH time is cutting into my actual playing time. Every time I log on, I usually end up spending 30 to 60 minutes on my bank alt. Plus I've gotten to the point where I have to use the mail system to store about 50-75 messages full of items because my bank and guild bank are full, so if I don't log in to move mail around, a few thousand gold worth of attachments could expire...And it's like pulling teeth to get Blizzard to restore your mail if you've already requested it a few times in the past.
...because I'm so hella smoooooth.