Most adventurers will shoot for the "Comfortable" lifestyle (small cottage or private room), which is 2gp per day. So the PCs go on an adventure for a week and each returns with 600 gp. This means they can enjoy the good life for 10 months. After that, they have to go at it again. If you keep this rhythm, the PCs are going on an adventure almost once per year, which might be realistic (if not exactly exciting).
You might couple that with Training, adding another 250 gp to the cost above, and the PCs will spend 850 every 10 months, and come out of their downtime with a new language or tool proficiency.
This assumes no yearning for power and influence in the world besides just "kill stuff." Become a Lord, or Bishop, Guildmaster, Headmaster, etc involves a lot of expenses (that you really create once and just becomes a per day/month/year for your campaign) and the player does not just get role play bonuses, but reasons to adventure and hirelings that can do stuff for them (maybe even be lower level PCs to send on minor adventures because raiding that three cave system is just too petty for the Baron of Westmarshwilderlands).
Gold is awesome. Characters have needs. Need to bribe someone? Gold. Need to travel by ship to the Green Isle? Gold. Need a resurrection and your characters aren't powerful? Find a powerful cleric give them gold/quest. Tired of traveling by foot? Gold and you have a horse. Find too much crap to carry back to your lair? Glad you spent that gold on the mule. Your mule was eaten? Buy another one.
Social and Exploration pillars make gold vital. Even in combat gold enables better equipment. Sure, you topped out on your platemail and your fancy but non-magical sword that your DM decides is keen and so +1 but not magical. But you are about to attack a huge fortress and their are four of you with a beast companion and a familiar and there are about 500 goblins living there. You have tons of gold and they will fight you and kill your families (whatever, this is just a quick thought).
You go back to town, say we need a couple catapults, etc and 50 of your finest men/women/whosists and we are ridding this land of that Goblin horde.
Gold is for whatever you want to spend it on and you're going to get a lot of it. Your character probably has dreams that involve money, nearly everyone does.
The party I DM for is a mix of 7 players that usually only has 4-5 drop in at a time. It is episodic. They vary only from 2nd to 3rd level and they've only gotten a few GP each. They are left wanting more, because they are starting to worry about how they'll repair their stuff, replace ammunition, etc. But they're in the wilderness, why would a raiding party have 100% of their wealth on them?
They'll find a lair soon and then have more than they can carry. Tough choices to come.
