A general misconception is that the introduction of gems alone will cause inflation in the gold economy.
The gold economy is based on gold entering the market through mob/pvp drops in various forms, through gathering and processing of materials and through event completion rewards.
Gold in the market moves around between players. This unlike in the real world doesn't create more money. In fact it removes gold from the economy through fees on auction transactions and ingame mail. As a comparison this is the foundation of which poker sites business model is build. Taking a piece of the pie every transaction.
The gold economy is thus an almost closed loop. I'll get into the "almost" in a couple of lines.
Gems enter the market as an representation of items. A list of the items that can be bought for gems can be found here: http://www.guildwars2guru.com/forum/...9.html?t=32319
Trading 5000 gold for 50 gems will not directly create gold or gems in the market. In fact it will remove gold.
The player that had 5000 gold before, now has 50 gems minus a gold transaction fee.
The player that had 50 gems before, now has 5000 gold minus a gold transaction fee.
Gems will however due to some of the buffs you can buy with them create inflation, though not directly.
For gems you can buy 20% Karma boost for an hour, and 10% larger chance of finding rare items for an hour. Items bought with Karma might be vendored I don't know the details for this, but rare items will be worth more than normal items. You can therefore pay to change the drop rates.
Other ways Gems will impact the gold economy is everything in the shop that you would have spend gold on but now can buy for gems.
Repairs, Resurrection, bags, loot bags.
This is because that equipment you wear should be seen as an expense. So items you get from gems will save you gold or karma.
In the end inflation comes down to how much gold enters the economy and how much leaves the economy. Perceptible inflation comes down to the individual. Some may find they have an abundance of gold while others struggle.
Gems can serve as a redistribution system, as people who are clever at playing the market ingame will be able to acquire items that cost real money but trading them for in game gold. And the family dad that want's gold for WvWvW schematics can indirectly trade real money for gold.
Prices will adjust overtime. Both the gold and the gem market will have to ensure enough ways for them to exit the economy or else we will see inflation. The Gem shop is mostly filled with consumables and this is a good thing. If it was items you only bought once the gem market would become stagnant and overtime the value of a gem would drop.
All in all I think the introduction of Gems is done very clever. The real test of time is the games ability to balance the 3 currencies, Gems, Gold and Karma against time played and real money. This will require good gold sinks. I hope they get it right