The top 1% wealthiest players control a mere 24.25% of the game's gold. Half the people who answered the survey had at least 35,000 gold. However, the bottom 75% of players controlled a mere 14% of the game's gold. This describes a huge disparity between the top gold earners and the bottom.
This isn't really a surprise, though, when you think about gold in game. In WoW, you are perfectly capable of running out of things to buy. There comes a point where additional gold no longer serves a purpose; unlike real life, where you can always buy bigger, fancier, and more expensive things, WoW has a high-end value cap. Gold becomes a goal all on its own. If you've got 35,000 gold in your pocket and you've already bought everything you want, what would you do with still more gold?
The survey results are interesting to read and definitely worth your time. But keep in mind that that roughly 2,500 people responded. The total number of players is more than three orders of magnitude greater; be careful about what conclusions you draw.