In game mechanics, we make account to the gold gain / hour for each stage, for example:
level 100 monster drop countMax 30 gold coins
level 1000 monsters drop countMax 90 gold coins
there is an increase rate here so as your level increased x10, your gold gain increased x3 which around 3% increase per 100 levels
therefore : by being aware of the gold collecting rate at constant level and increase rate, you would be able to move to the next part
Gold sinks:
Gold sinks are pretty much how they seem to be, it is system in-game that requires gold and keeps increasing in the gold needs some server made it used by waypoints system others used rebirth npc
for me i created multiple currency in the game play and each npc had his own currency depending on the kind of the system that he gained this coins by
increasing support to the main game currency from the other sub currencies creates the illusion in the sub-conscious that this is something value-able which if you didn't do players can ignore it till they know its worth, you don't want people to complain about what they throw you are allowed to build this illusion ethically..)
At this case above you can't make gold buyable by those tokens from NPCS, because this will happen through players economy and interactions which starts the pricing and the real worth is being defined by players without GMs having any opinion about prices.
because nowdays i see owners control items price in gold which feels too idiot to me.
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This is just Example on how to make demand higher than support.
And just 1 store that uses gold to buy upgrading materials that can fuse, make your EQ stronger
gold needed for 1 item increases as the item you want is rarer so you are mathematically calculating how much demand points is needed for this currency is slightly above the support, idk if i was clear enough to explain it its not simple nor complicated and im idiot when it comes to explaining something. maybe i can talk about it freely in chat 1 MSG me i might give you some ideas on building an economy for your server that allows player to have common sense about equipment prices, and gold to be really useful and high on demand.
(Currency Support = what the gameplay gives in loot/system/bosses .. anything the server gives regarding the currency is support)
Currency Demand = how important is what this currency can be used in)
You create support and create demand slightly higher for example if at level 1000 player should have looted (free) around 30-50 crystal coins
then your currency support at this case is 30-50CC
therefore demand should be slightly higher average of 55-60, currency or anything worth is based on being needed more than given
(Demand >> Support == Worth)
last tip : when you get to calculate things in game mechanics you suppose that everything is always max (CountMax = 30) then count is always 30 to make the gameplay challenging by default and with respect to your mechanics