Persistent piggerbacker

How do I deal with a persistent piggerbacker. I need the buybox specifically for this one item for positive metrics. I manually adjust the price as needed and it doesn’t dig into the margin that much. However this one seller is piggybacking this item down and won’t let it go. I know what this item costs wholesale, so like are they just selling at a loss for fun? Bullying me to drop the item from my store? I don’t get it.