There were so many bots with a ton of tokkul on their accounts with not enough for a onyx so the botters bought obby capes. Plus there are so many in the game that they are going to stay around the price they are now.
Before you could bot a 99 in like 2 days and wear that cape.
You really can't anymore. So it MAY go up as new players show up.
I think its a bad investment though.