Gems are only created when bought with cash or were seeded in the exchange when the game went live and destroyed only when used to buy something from the Gem Shop. Gold only comes from various activities in the game as rewards. The exchange creates neither Gold nor Gems.
Gold=>Gems have one purpose and that’s buying items from the Gem Shop. Buying Gems with cash however has two purposes, either buying items or act as an intermediary step to buy gold, that was already in the game, with cash.
The two exchange rates are locket at 72.25%. That’s 85% squared. This implies the exchange sinks 15% of the gold going in and coming out of the exchange. It’s no different than the TP, 15% off the top of every completed transaction. The gap also discourages the use of gems as short term storage of wealth as well as discourages attempts to manipulate the rates. This percentage gap was always there, back when you could buy 100 gems for 1 gold, 5 gold, 10 gold, etc. it was ever present.
The exchange in theory is simple. There are two vaults, one holding gold, one holding gems. They were seeded at the start of the game such that there was a lot of gems but very little gw2 gold. Now the two vaults are always of equal value. As gold is added and gems remove it makes the remaining gems worth more. Add gems and remove gold, gems are worth less. It’s that simple. And simply more players are adding gold and removing gems than the other way since the game started.
The only way ANet affects prices is adjusting what’s in the Gem Shop. The rest of the time it’s the notion we can get something for nothing that drives players to dump their gold into the exchange for gems to get that new/returning/on sale item. The current surge in the rate is solely due to long missing but desired items returning and the rush of players wanting to get them for “free”.
Why would any one want to convert cash to gold via gems? Because if you have money but not tons of time to spend in game, a $25 gem card buys you 200+g right now. This isn’t new gold but gold other players game up to buy gems, gems that are now refilled with this exchange. True that you could get more going to “dealers” but this way you won’t get banned, cheated or your account stolen.
And you know what? At midnight PDT when the next set of sale items hit, there will be another surge, depending what returning or items put on sale are added. As long as players have the gold sitting around that could be converted and as long as there’s something at the shop they want, the rate will keep ratcheting up ever higher over the next 10 days.