In a fairly generous campaign, I think we hit a peak of about 40,000 gold for 5-6 players around level 14. However a number of items were magic items dropped as loot, so never really became part of the gold currency valuation.
In a much less generous campaign, we peaked around 6000 gold for 6 players at level 10 (group funds, plus wages for a ship's crew). Almost all gear of any significance was purchased, and spending 3000 gold for an item involved a group discussion to agree it was worth using up the majority of the communal funds for one person. We also had just hit a point where our cash cow (the merchant ship) was about to become a liability rather than a source of income.
In a third campaign, we struggled to buy a few diamonds for Resurrection material at level 14 (because we usually needed to cast Resurrection at least once per session). Money was almost non-existent.