I think the problem lies with the enforcement of rules against gold selling. In terms of games where gold is strictly obtained in-game, the duty falls to the developers to create ways to keep gold sellers from operating.
With that said, gold sellers will always find a new way to get around smart developers. In WoW, recent changes have brought right-click reporting and auction delivery slowdown into the mix. Even with these, however, gold sellers are still thriving.
I don't think that there is a way around it without designing other ways of attaining items and marking achievements. As long as high-cost items stand out of the reach of casual and less-than-hard-core players, these things are going to happen. The only solid way to prevent gold selling is to make gold bound to a character. Oy, come to think of it one could still give out one's password like certain power-leveling services. It's impossible.
The latter part of your letter deals with economy issues that developers have to deal with. The hand that giveth taketh away via auctions, minigames, and who knows what else. Most developers just don't devote time to it.