How long was this? I can see it in the early years but I'm wondering if it can be done now in WoW today? Which is probably what the OP wants to know as well. And no, I dont have any interest in doing this. Just curious if you did this back then or recently.
I'm going to guess it'd probably be extremely difficult, and heavily dependent upon your server. I've never tried to fully corner an AH by buying out, but I have tried cornering markets through my toons (all profs at 580+ except inscription), and it just doesn't usually work anymore due to large numbers of people trying the same thing / people with lots of alts.
If you're going to do it you're going to have to expect to lose money from people like me, because I gather my stuff just through every day play, and since I'm not buying things out, I don't really have any money invested to lose.
For example, on my server I tried forcing my way into a couple markets -- belt buckles, flasks, cooking mats, golden lotus, etc. I had a banked supply, so I could put 3-5 up each time I undercut, but there were 3-4 other people in every market I found/tried that would undercut me CONSTANTLY -- I'm talking within 10 minutes, every time.
We took belt buckles from 600g per to under 300g in under an hour. I tried listing perfect cut green gems for 45g each, no matter the cut, and we'd be down to ~25g in no time. My break even was something like 10g/gem, I don't care.
Eventually I found that nobody else was listing 100 year soy sauce, I could get 4 / day from my toons. Made ~15k from those in about 2 weeks, then they started catching on and I saw spams in /trade and VotFW /general that they were buying for half of what I was charging, and then they started undercutting me. I started listing mine for under what he was paying people, so he started buying mine and I'd get more back up right away, though for slightly less each time so he'd keep buying me out. I brought them down to 75g per, let him reset the prices, and started all over again at 125g, though he figured out what I was doing, quit buying me out, and just took the hit until I left.
Tiger Gourami was selling for 300g per 5 stack due to the cooking quests and none on the AH, same people started showing up with theirs after a couple weeks and brought it down to 7g / fish. Gave up on that one.
Only thing I still do is golden lotus. I plant enigma seeds on 2 characters/day (do songbell seeds on the other 2 for now), so I get between 7-10 golden lotus / day for 10 minutes of "work". Tues/Wed/Thurs I list individually for market price (95-97g), sometimes they sell sometimes they don't. Fri/Sat/Sun/Mon I just save them up and list whatever I have in 20 stacks on the following Tuesday afternoon for 40g under what this guy sells his flasks for. One of two people snatches them up ~4:30pm server time, I can get rid of 2-3 stacks at a time for 1800/stack. If I don't see any flasks up from 2 certain people, I'll try to sneak some of those in there if it's just before 5pm server.
Not gonna lie, I miss the days of 200g per mongoose enchant. I made 12k in an hour once just by standing on the IF bridge when the shattered sun vendor opened up.
TLDR: I don't NEED gold for anything, but it's kind of a mini game to see how many people I can upset in the process 