Why does gold cost so much?
Because the population as a whole actually does think that these are decent rates to convert Gems → Gold at.
Since April, the ratio has remained remarkably steady. This means that there’s roughly an equal amount of people converting Gems → Gold vs Gold → Gems. When people convert Gems → Gold, it makes Gems “cheaper”, and vice versa for Gold → Gems (Makes gems “more expensive”).
If enough people thought that the Gems → Gold ratio is too low, then they will not do it, and Gems will get more “expensive” (lowering the “cost” of gold via gems). But you don’t see that. Thus, it can be inferred that enough people find the rate acceptable.
Currently the gem chart at GW2spidy is broken for some reason (at least for me). The one at GuildWarsTrade is working but it only shows the Gold to Gem rate. The Gem to Gold rate is 72.25% of that.
http://www.guildwarstrade.com/gems
As for the OP, the Gem to Gold rate mirrors the Gold to Gem rate and as as long as more players by Gems with Gold than vice versa, it goes up. Otherwise it goes down.
Spikes up happen when something sexy goes on sale at the Gem store and then usually decays back toward the pre spike value.
Expect the next spike when the infinite logging axe comes out unless they put bank and inventory slots back on sale before then.
RIP City of Heroes