It's not necessarily constant undercutting. Prices drop as supply increases due to increased farming, or demand decreases due to saturation of the market. Prices have to be able to change with supply and demand, otherwise the market would cease altogether. It's pretty much basic macroeconomics.
This item is currently being tampered with on the auction house on asura. Inflating from 25k to 320k. Users contributing to this are: Cresen, Tasume, Naten, Aiden, Mitsuke, Darkfall, Poprin, Renamo and probably more. Buyers beware. I believe all 10 rings on auction right now are inflated at this "new price".
