There's an annoying UI quirk that makes people less likely to buy mana crystals. I particularly notice this with Fblthp's Findings. If I'm looking at the available purchases in Fblthp's findings and I don't have enough crystals to buy one of them, I can't actually see the card to decide whether it's worth spending real money to get the crystals for it. The user can only read the card if they already have enough crystals to buy it! There is a way around this -- write down the card names, go to my card collection, select Show All Cards, and search for those names -- but it's way less convenient and this is probably costing you some sales.