Guild Wars 2is free-to-play after you purchase the game: There are not recurring monthly fees. The game will have the Gem Store, though, an item store intended to bring in extra cash for NCSoft and ArenaNet, the publisher and developer of GW2. Some gamers will never use the item store and others will spend money there like a derivatives trader on speed. Most will fall somewhere in the middle, occasionally stopping in and spend ten dollars every month or so.
So what’s in the Gem Store? There’s nothing that will imbalance the game. It’s mostly convenience, vanity and some account items available for purchase. A little sampling of what’s in the Gem Store is listed below:
Dye pack 200 gems 7 random dyes, 5 common & 2 uncommon
XP boost 125 gems 50% XP bonus from kills for one hour
Pirate’s outfit 700 gems You know you want one
Bag slot 400 gems And additional bag slot for all your loot
Minis pack 300 gems 3 random mini pets, 2 common & 1 uncommon.
The complete list* of proposed offerings, along with the item description and gem cost, is listed here. This list is a pre-release list of proposed items available in the Gem Store. It might, and probably will change when the game is released. Still it gives you an idea of what’s going to be available and what you might want to spend some money on.
(*Source: Guild Wars 2 wiki.)