Why does price of gems change when you buy them?
Because ANET’s algorithm determines the prices. How does it do this ?
ANET won’t say.
When I pull up the currency exchange tab it says the average price for 100 gems is 57 silver. Then, when I click on trade gold for gems it switches to 100 gems for 77 silver.
There are two rates, with about 30% difference between them. It costs more gold to buy gems than you will receive if you sold the equivalent number of gems.
A little logic here… if Anet charged the average price, then by definition the average would never change.
There is clearly some goal in terms of sales volume that they want to track (what precisely the goal is, can’t quite say, but the goal is not to maintain the average). When sales are high (over goal), they will bump up the price to extract higher margins and prevent a glut of gems. When sales are low (under goal), they will lower the price to attact more buyers.
The average just tells you what the trend is when compared to the current price. It might go up or down, it might be moving slowly or quickly.
In otherwords, its like the stock market. If you’re smart, you can find ways to manipulate the hell out of it, buying low and selling high. I’m sure many people do.