[intended]

Adding to gold sinks -

WoW I think had some of the most visible impacts in terms of gold sinks (some I am sure were pioneered by other games and MMOs)

They brought about the concepts of vanity items, which were absurdly expensive and went from there.

Whats even more interesting is seeing the progression and evolution of these economies.

Wow 1.0 auction houses and others barely had the concepts of gold sinks, nor any of the finer tuned economic catches that blizzard introduced by the time it reached its 3rd expansion - Wrath of the Lich King.