There's been a kerfuffle between Guild Wars 2 community and developer because of a patch that made surprise - and unfavourable - changes to the gem Currency Exchange.
Gems are used to buy cosmetic and convenience items, and can be bought either with real-world money or in-game gold.
Pre-patch you could spend custom amounts of gold buying whatever the equivalent in gems. But post-patch you could not. Now you can only by gems in set quantities, 400 being the lowest.
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