Agreed with Akin. Gemstones are way harder to get than the other OGH mats, they require you to farm a harder instance multiple times and when you reach level 10 challenge you get 5-20 gemstones per run, unaffected by bbg.
The price should be 10 coins, unless your goal is to kill the market price of gemstones in which case I disagree because the game needs those alternative farming spots.
