Gil sinks cannot ever take more money out of the economy than is put in because it creates sections of players who no longer can afford to advance in the game. In that regard, gil sinks act to slow inflation, but they can't stop it.

The game's economy is so bad that it needs massive intervention in the form of tiered redistribution.

Someone needs to do some statistics, remove all the gil from the game, and then hand out money based on relative wealth until there's an acceptable level of gil in the game so that everyone keeps their relative wealth based on the new in flow of gil, but also so they will remain in their position of wealth without taking a disadvantage. It's rough, certain people would quit, but it's the only way to permanently fix the economy without resetting it completely.

It's a major problem.