If you are wanting the prices to go down then go out and kill the bosses your self and get them as drops, granted you won't always get what you want, but you wouldn't have to pay. And if you can't go out and kill them then I'd say your stick with other ppls prices. We only charge so much because of what we spend during the battles, idols and whatnot. One more tip: just get the warden then upgrade it then lvl til you can get frozen so you won't have to be paying for diamond or qaurts.
Ahah! Here lies my point. You need to get them yourself or pay the price that someone is charging for them. I have a ton of discs because I buy rest pots, and then solo the bosses and usually I sell the discs for these prices.
Moon- 1k
Sun- 2k
Oak- 5k
Elm- 8k
Crown- 10k
Drag- 50k