Currency Exchange
The exchange gives you what is listed on the “Average” amount. Why? Because what the exchange does is, if someone isn’t buying gems, your gems are still sold to the server in a pool, and the server gives you the in-game currency as per average. Vice versa also works. This way, there will never be a shortage on the Currency Exchange of either currency. The server auto-adjusts the average based on supply/demand rules.
At least, that’s how it looks from the GUI itself.
The short story is that investing in gems is a good long term investment, but usually a terrible short term one (with few exceptions since the game launched). To see historical rates, check out gw2spidy.com
There are two different issues you ran into. The first is that there is an implied tax when you trade coin to gems and gems to coin. Your net loss is approximately 32%, as if you paid the 15% trading post fees on each transaction. In other words, if you start out with 1 gold and buy gems and then turn those gems instantly to gold, you’ll end up with closer to 70s (my math is oversimplified, but it gives the right idea).
The other complication is as you suspected, the rates can change drastically. Over the course of Wintersday, the coin→gem rate varied from as low as ~1g50s per 100 gems to as high as ~2g25s, so there are better times to invest than others. During the same period, conversion in the other direction ranged from 100 gems being worth ~1g13s to ~1g70.
Since many MMO-veterans believe that GW2 economic inflation is inevitable, they recommend that you convert some portions of your coin into gems. That’s good as a hedge against coin decreasing in value relative to its purchasing power.
So, over the course of Wintersday, if you bought 100 gems at the lowest rate of 1g50s and sold at the peak of 1g70s/100 gems, you would have made 20s off your initial investment, a 13% investment. Personally, I never managed to be online for the lowest rates — I managed to buy 100 gems for 1g70s, meaning even if I sold at the highest rate, I would have merely broken even.
Accordingly, my recommendations are:
- If you want to buy something in the gem shop (like a new character slot), then look at Spidy for a good rate over the last few days and try to buy gems at that rate.
- If you want to invest against inflation, buy gems whenever you can afford them and the rate is good relative to recent market.
- Be prepared for spikes as soon as an event is announced or begins and dips as the market adjusts.
If that rate goes too high, and you have enough real life money, you can always head to gamestop and grab 1200 Gems via a card (It has tax. If Walgreens offered it, it likely wouldn’t, as it’s same-exchange money per good, like the steam wallet cards.)
But I suggest taking Was Na’s advice until that happens. I may get 2-3 cards a month so I can stock up on Gems for future higher markets. Or if a gem offer occurs, like a specific mini pet, or costume.