The amount of content they produce for an MMO-style game without a sub fee is kinda crazy. Do they have microtransactions in the game? If so, that would explain where they're getting their money.
They have a trading post. You can buy mats, armor, weapons, trinkets, sell stuff (certain things, not all). You can purchase gems which is what you use to get stuff like repair cannisters, mining items (pick/axe/sickle when they have promotions on those items), skins (change look of your armor), minis (mini versions of creatures/npc's) that follow you around, etc...check the main GW2 site as it goes into detail about a lot of this stuff. I've dropped a fair bit of cash due to them changing the # of nodes of 2 T6 materials (ancient saplings and orichalcum ore) which are needed for crafting exotic armor/weapons/trinkets (rings, earrings, amulet) due to bot farming a while ago. It seems they added a few more of them to certain maps (they are only available at a few maps). So lots of grinding for those and they are time-gated (once every 24 hrs that you dig/chop/pick them) to I guess balance the economy. Same for a couple of other things that I got for completing some living story stuff (quartz crystal node in home instance map, candy corn and watchwork sprockets) and those are daily/24 hr wait items once gotten. Feel free to PM me if you want more details. I enjoy playing it, the zergs in WvW/Edge of the Mists can get crazy/annoying. Dungeons are brutal, Fractals of the Mists is also brutal/intense/hard.