So, on my server, there are people handing out Iron Clappers by the NPC that asks for them since the start of the event. They are great and awesome, but still some people use the marketboard.

I decided to check the price on the marketboard for the clappers and, lo and behold, they were 4900 gil. Wanting to make them available at lower prices, I crafted a bunch and listed them well below that - only to have them all bought up immediately, all by the same person.

This kept happening - to my clappers and to any others that were listed as basically freebies. The people buying them out didn't even have Blacksmith leveled - they were just buying to resell.

Thus I decided to ruin their day.
In order to ruin the day of those people in your server, you will need:
1.Blacksmith at least at level 15 (to craft the clappers);
2.Fire Shards;
3.Any vendor that sells Iron Ingots (e.g. Amalj'aa vendor, Material Vendor in housing areas);
4.Any vendor that sells Undyed Cotton Cloth (I use the in-house Material Supplier);
5.The means to sell clappers on multiple retainers (at least two, preferably more, if you have more);
6.Some gil to invest;
7.Lots of free time.

Now, buy a good 3 full stacks of undyed cotton, iron ingots, and have a good 300 fire shards in your possession.

Now, craft. Craft clappers. Craft at least 40 of them.

Now it begins. You see, if you just list the clappers at very low prices, a reseller's just gonna buy all of them and place the market right back where it was, preventing the people who could actually use them from buying them cheaply.

No, you have to artificially lower the price. You have to undercut. Undercut the highest price by 100 gil. Then in your next listing, undercut yourself by 100 gil. Continue to undercut yourself until you run out of retainer space.

Then watch.

Watch how high the reseller is willing to buy your clappers at. Did they buy all of them? Good. Relist everything using the exact same method. Craft more as needed.

It won't last long before they notice something's up and start lowering their prices or stop buying from you.

If they start lowering their prices, adjust all of your listings to be lower than their listings, and undercut yourself even lower.

Are your clappers still being bought in bulk? Good. Now, once they stop trying to list clappers at lower prices, you have to change your tactic. Stop undercutting yourself. Put up listings close to the highest price some other guy is selling them at - in my case, someone was selling them at about 880 gil, so I put my listings at 800 gil. I listed dozens of clappers at 800 gil.

And they were still being bought in bulk. Repeatedly. Over and over, the same guy bought them at 800 gil.

Eventually, they realized I wasn't going anywhere, and they probably realized they now had stacks of clappers with my name on them, and that they had to get rid of them somehow.

So they started undercutting my 800 gil listing by 1 gil. They were undercutting me with my own clappers.

Thus I changed all my listings to 700 gil. Then they relisted at 699 gil, which I promptly undercut to 600 gil. Then 599. Then 499... you get the idea.

When they listed at 199 gil and I undercut to 100 gil, their soul was finally spent. They gave up. My clappers were still being bought by some people in bulk, but mostly they were selling slowly, likely to people who actually needed them.

I walked out of it 100k richer, most of it money from the guys who thought it'd be great to try and buy me out.