In the latest pre-patch a new system for buying gems with gold has been introduced. You can no longer buy less than 400 gems via gold conversion.
From the top Reddit comment: "A player who doesn't have a lot of time, but has a lot of money (they have a job) buys gems. They buy 800 gems and purchase a 500 gem item. They have 300 gems left over. Then, they decide they want to purchase a 400 gem item, but they need 100 more gems. On the new system they cannot only convert gold into 100 gems, they need to convert at least 400 gems worth of gold. But they don't have that much gold, and because they don't have a lot of time to play, they can't farm it (and 400 gems isn't cheap, it's over 75 gold right now). Thus, this person must spend more real money on actual gems, at a minimum of $10 for 800 gems, even though they only wanted 100 gems."
Basically ANet wants more of your money and there is nothing you can do about it. Thoughts?