The only way to eliminate illegal RMT Botting, and illegal gold selling to cheaters that buy gold is to eliminate the need of gold itself at the start of a Fresh/SOM2.
Reduce the cost to buy things in game, or eliminate it completely but increase the questing involved to obtain items: riding, flying, dual spec, mounts, raiding enchants, professions and unlocking secret patterns/formulas/skimatics.
For example
Make fast flying skill 50g down from 5,000g and attach a quest chain that requires 2-3 friends to complete or an aerial obstacle course to unlock.
Dual spec is 10g to unlock a trial by fire quest of defeating 10 rounds of NPC in 2 spec.
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Bots don’t clear raids so make more personal loot a thing and make raid gear and enchants attached to a badge/emblem currency and sold only to NPCs.
We are here to adventure and conquer monsters with friends so make that a priority over the acquisition of gold and buying our way to purples. Team building quests to gate keep content that was once purchased with gold/CC.
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Blizz has had 20 years to fix the economy but they can’t fix all you cheaters, and should NOT have to. Reduce the need for gold in place of questing, personal loot, badges etc and you’ll have a healthier economy and healthier player base.