Comment by cge

> But as they can't easily (i.e., without expense) A/B test their strategy

There also isn't really any detriment. At worst, the sniper is making the same bid they would have made otherwise. If the opposing bidders are not purely rational, and have not put in their actual maximum bid, then sniping can deprive them of that opportunity and thus lowers the hammer price.

And bidders are not purely rational, especially when the items are not purely utilitarian. Getting notifications that you have been outbid has an emotional effect, as does having time to think about raising the bid.