How do you react to being undercut?

[Rrylia]

You can /tell retainers now?

I don't think it's that - but for many items the name of the crafter is listed at the bottom of the item, so it's pretty obvious who owns the retainer(s). Also worth noting if you are trying to manipulate the markets (tut tut) because you will appear as the main buyer and as the crafter of all those overpriced items. You can however recycle the items (trade) to get rid of that.