Those are rates that I remember that were the current rates when I last played, which was quite a few months ago. Perhaps Gaia was just too lazy to actually look up current rates and just had these numbers remembered?
Iron treasure chests have sat around 10k and Gilded have sat between 30-40k (meaning, fluctuating up and down but normally resting roughly around there) for over a year.
Source: I am a loser who used to used chests for profitable T to G conversions and they deflated in Gems (not to 15k) but I still have a huge inventory of them, so I wait for them to increase and sell off 2-3 at a time.
Rusted isn't too bad - they tend to sit around 2k. Won't talk about ore, I have no idea.
(Sorry for stupidly long post, I'm just really angry at Gaia)