Merchants: Tisiana at LS Dru Circle sells you different items than you buy

[Omnimorph]

It charges whatever the item is that gets moved up on the vendors list. So if you click on say a 5p item, and all of a sudden someone buys something else from that vendor without you refreshing the vendor window, it'll move up whatever is below that (not sure how it orders this, server side) so if the item moved up costs 200p, you might end up trying to buy that.

At least that's what i think it does. Maybe a dev could clarify this.