Ascetic rewards (trophies, haircuts, greetings from NPCs...) is indeed a good way to get a lot of gold out of the economy. Many people already have commented on that, so I'll expand on gambling, as it is a mandatory way to get gold off rich players who don't mind having a dirty armor and an empty guild hall.
First of all, gambling means burning something valuable such a gold, items or materials in order to get a random effect. The important word in this sentence is random. In all games including GW, you want to play the game and to be rich, and your wealth will increase your intrinsic power. There is no such thing as "100% skill, 0% grind" unless the UAS is used (which would be a lot worse for the community and the game as a whole). If two players are equally skilled, the richest player will always win. Runes, and perfect items will make you stronger.
So why is gambling a good thing for game balance?
Because using random rewards is just a way to reduce the power/wealth ratio in the upper layers of the game economy.
A good money sink is designed to get gold and items off rich players, not from poor weaklings. Veteran players already have gathered many runes, items and they have the most expensive armors/weapons in the game. The random reward ensures they can get some ultra-rare <whatever> that few other people have. Why does it have to be random instead of a fixed but exensive item (such as 15k armor)? Because gambling is addictive, and especially to players who have a lot of gold, and a lot of spare time to farm and to get more gold, or to PvP extensively for PvP rewards.
With gambling, you give useless to average rewards most of the time (read: acceptable for beginners and junk for rich players), but once in a while gamblers will get some very rare <whatever> that they can sell to keep gambling, or burn for their own use.
If the gambling fee and the reward are finely tuned, you remove gold from the economy and you inject only little wealth in return. This feature is good in that it doesn't needlessly hinder the average gamer, and it removes a lot of gold from top players. To that extent, it is the contrary of bags or ID/salvage kits. These are removing a marginal amount of gold from the economy and they are only affecting poor/average players. That's why they are very bad money sinks.
What would players want to gamble for?
- Random ascetic rewards: I know many players who would burn dozens of thousands of gold in order to have a unique and stylish weapon, armor aura or whatever. Just have a look at the popularity of black dyes, chaos axes or dragon swords. How does it translate in game? Example: Add a NPC able to randomly enchant your weapon and to change its look. 0.01% of the time, you can get a cool and very rare glow similar to chaos axe or collector edition emotes. With such a gamble, many players would burn gold, looking for stylish weapons, and very rich or very lucky players would get an ultra-rare collector weapon. Meanwhile unneeded gold is removed from the player economy.
- The perfect + epsilon item: burn gold to get a reroll your sword's mods from a crafter NPC. 99.99% of the time, you get average to good mods. Once in a while, you can hope to get very rare and valuable item such as a 15/23 sword or 17AL shields, in addition to existing mods. The ingame power of this rare mod should be small enough for casual or poor players not to be as disavantaged as when lacking superior runes or rare skills. Yet rich and competitive players would gamble quite a lot of gold in the hope of getting a perfect+epsilon item they can't buy/craft. As a result, you drastically reduced the wealth/power ratio. You have to sacrifice mountains of gold for a very small result. The power of gambling + diminishing returns.
- New quests and missions: create areas similar to UW/FoW and make them impossible to enter unless you give special items (let's call that kudzons) as entrance fee. These PvE places have average drops but they give good XP, as well as quests for elite skills (which you can still capture normally).
Each place require a kudzon of a given color. Some kudzons are common (eg: pink kudzon), some are rare, and some are incredibly rare (eg: black kudzon). You can get one of each kudzons from quests (to ensure that all players are able to play in these areas), and you can get common/rare kudzons from collectors.
Average players can visit these places at least once with fixed kudzons, and they don't need to play these areas repeatedly to enjoy the game. Grinders (read: people enjoying grind) can happily farm for kudzons and sell them to other players. Rich and lazy players will buy black kudzons for a good amount of money (thus only transfering money from one player to another).
Now let's add gamble in that. In addition to this 'fixed' way to get kudzons, add a NPC which sells random kudzons for a relatively high fee. Most of the time you would get common kudzons but once in a while you can get an ultra rare black kudzon. Casual players are not affected if they enjoy their own kudzons, and since black kudzon area won't give them anything special. Rich and lazy players who want shortcuts can get better XPs and elite skills (or just cool PvE sessions) with black kudzons, so they gamble and ditch useless kudzons. Gold is removed from the economy.
The new quests & areas do not bring anything into the economy. They only provide a shortcut for experienced and rich players. Faster leveling for alternate PvE characters, skills unlocked more easily. Casual player can play normally and go to these places once, while playing the game normally. However the main way to get to these places repeatedly is to gamble and therefore to burn gold. Rich players get a boost from their wealth (as usual) by being able to use shortcuts, but the power/wealth ratio is reduced.
- Unlocking: many PvP players are complaining about being forced to play PvE again and again to unlock skills, runes & components. This is also true for PvE players. Why can't I start playing my new W/E with the ubber Ice Spear I have unlocked with my ascended E/Mo?
After the last mission, add a NPC able to unlock skills (or component/runes for PvP only) in exchange for an item (kudzoo) that you get in PvE (quests, missions, and random drops) as well as in PvP (especially as consolation prize if you lose the game). You can get 'component kudzoos', 'skill kudzoos', and 'rune kudzoos'.
By playing the PvE game normally, you'll get enough kudzoos to unlock what you need for a few extra characters. If you want to PvP only, you can unlock stuff by getting kudzoos in PvP. If you want to unlock more or faster, you can grind and burn your wealth to buy kudzoos from a gambler NPC. Pay a few thousands of gold and you may randomly get a component kudzoo, or a skill kudzoo or even an elite skill kudzoo. Gambling is not mandatory here, but it adds a small addictive reward for players to come back and gamble for more.
Now to make it an efficient money sink, kudzoos could unlock things only temporarily, such as 24h of play time. If you don't want to play PvE extensively, just use your gold to buy kudzoos to keep your favourite setup unlocked. Gold is removed from the economy.
Conclusion: gambling is good as long as it provides items that you can get in a fixed way by playing the game. Its purpose is to provide random shortcuts to rich and lazy players who have completed all missions, as well as to promote trading between players. Using random rewards is just a way to reduce the power/wealth ratio. As long as you can still obtain what you need normally, gambling is a good way to remove gold from the player economy without injecting anything good in return.
I hated that, lol.
