That's the thing about GW2, you can't trade with other players. It all goes through auction houses. Gems can't be sold to players, only to the game. The exchange rate is always changing too. It's also very easy to get good gear. Once you hit level 80, you can run a 10 minute dungeon and get tokens. After 2 or 3 runs, you'll have enough tokens to exchange for an exotic piece. So even if you buy gems and exchange for gold, you're getting ripped off by a lot. I just checked and 800 gems is roughly 30 gold right now, which is $10. A decent exotic costs around 5 gold with the better skinned and precursors going to the 400-500 gold.
Also, PVP is completely separate from the main game. Everyone can make any build with any gear in PVP. All you do there is win the skins and rank up.
In WVW it doesn't even matter what gear you have because if you stay with a large group of 40-50 people and fight with another group, you'll most likely die no matter what.
GW2 also has no end game and the main game is easy as shit.