Somewhere lurking in my (off-Amazon) promotion lists was somebody who would wait for us to run a sale, or would find any way to buy our products below our Amazon price through resellers, and buy as much as they could. Invariably, we'd have a great sales day or two, and then see dozens of units pop up in FBA from an unauthorized seller two weeks later.
First we tried contacting them. No reply. We explained to Amazon that this is an unauthorized reseller and could present a safety issue. Got the usual "Get control of your distribution chain" advice.
It wasn't often. But whenever they popped up on the radar, they always undercut us, removing us from the buy box, and killing the ads we had to the listing. With the ads gone, it took longer to sell their stock, and rankings dropped.
We keep our prices very controlled, and I'm not one to "race to the bottom." But on a whim I decided to see what would happen if I moved my price lower than theirs. And yep, they were using a repricer bot.
So I waited til the dead of night when sales volume is lowest and dropped our price to product cost. Sure as sugar, their listing was now $.51 below cost. I bought them out entirely and upped my price back.
Yeah, it opened me to risk. And I wouldn't have done it on a super high volume listing. But we haven't heard a peep from that hijacker since.
Cheapest stock replenishment I ever bought!