I'm currently paying 90k gold for 6 energy and I also know a person who pay 110k for the same amount and frankly this is just way too expensive.
Even if you say the gold is the cost of the guild chest, that's just dumb then. The guild chest reward doesn't really get better with relation to the gold you pay (unless a mod willing to correct me). Furthermore, sometimes the guild chests give you XP potion or express ticket which is useless (since you can get those two from somewhere much cheaper) and the gold from the guild chest is dumb (pay gold to get gold back?). The only good reward from the guild chest is maybe the job keys/energy/gem. In any case, if the gold is to justify the chest then it's a poorly investment.
If making the guild contribution a fixed price is impossible, then at least give out more energy for the quest. The current market rate for energy is 15 en for 40k gold but guild is 6 en for 100k gold? That's just too much...
Gold is already a valuable resource that's used for pretty much anything. I'm 3 months in and I still have days where I have less than 10k gold left. I don't think this "tax" is good and should be change.