The majority of the gil that has come into the economy is from quests, non-repeatable quests.

As long as there remains a steady flow of new players, this won't be an issue, but once the worlds mature and that flow dries up.. no more quests, no more gil from quests, which means a massively reduced influx of gil.

The economy should sort itself out, but what is worth 50,000 gil now, would end up being worth 5,000.. and that is fine for player to player transactions, but repair bills won't go down in price, they will only go up as people get better gear.