For many years I've played this game, and I've watched the economy fluctuate depending on many factors. There are many things that I've seen done in the last few years that are destined to make this economy inflate even worse than It is at right now.

Dynamis- This used to be a HUGE gilsink that was balancing the gil coming into the economy, and even sinking a bit too much gil. At 1 million gil a run per 10-64 people twice per week (Earlier groups would go in with 64, eventually you would see more 10-20 man groups), dynamis ate a lot of gil from adventurers' pockets, and delivered nearly zero items that you could NPC for something back. The little you could npc were crafting mats, as you couldn't even npc the mass amount of relic weapons that dropped like candy. Eventually SE decided it was a good idea to lower the entry to 500k, and lately they even changed the cost of entry to a one-time cost per person of 10k.

So with dynamis we went from 1 Million/10-64 people (25 estimated average) twice per week, to 10k/person once.

Limbus- This was a very popular endgame even though the cost of entry was a bit hard to handle at times for some. At first the price was 50k/person per entry. At 50k/person for 25 people this was a good 1.25 million/entry for a LS of lets say 25 people to go in. Eventually the price was reduced to 30k, and later it was reduced even more to 15k. There was little to npc from here as well.

So with Limbus we went from 50k/person twice per week, to 15k/person per week

Einherjar- Another twice per week endgame, this one was priced at 180k/lamp, usually 20-36 people per group. This one had a bit more NPC capability than dynamis/limbus, but you were still sinking gil back into the server with it in the end. This last update put lamps at 60k/lamp now

So Einherjar went from 180k/lamp to 60k/lamp, usually 20-36 people per entry twice per week.

The only other big example of a gil sink I can think of at this time is:

Femina/Vir subligar- These were really weird items priced at 8 million gil a piece from a couple NPCs in tavnazian safehold. Gilsink why? because they could be disenchanted into cashmere thread or shining cloths. People actually desynthed these for awhile since cashmere was so rare to obtain. This was around the inflation peak we had mid-CoP.

This last example of a gilsink we don't have anymore is a bit abnormal, but its something we really don't see anymore. We kind of need a way to get rare materials at this time from NPCs to dump the gil building up right now.

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Those were all gilsinks that have been reduced hard or removed at a time when we can make gil out of nowhere faster than ever.
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Heres a couple examples of where we are getting gil from that is driving this economy into inflation.

Cruor- Cool idea, there has been Conquest points, Imperial standing, Allied notes, and you could turn these into gil be it from auction housing items or NPCing them. Cruor takes this idea to a new and VERY dangerous level. At first people saw you could npc the teal/aurore/perle gear for a decent amount. Some 3000 cruor pieces would npc for 7.1k gil. However at this time most people hadn't realized the potential cruor you could make.

Chocobo Blinkers now are the most profitable way to turn cruor into straight NPC gil. At 200 cruor per blinker, they sell for 529 gil to a NPC giving us a 2.645:1 gil:cruor ratio. This could be dangerous or harmless to the economy depending on the rate of cruor one could gain.

Without being one of those people brag about how much X i can make per hour, I'm going to throw out a good simple number that isn't hard to reach. 100k cruor/hour is fairly easy to reach with a decent group in a decent camp with Atma of Royal Lineage (+20% cruor gained). This means you could have a group of 18 people in one hour making 100k cruor, in turn making 264.5k gil per hour, per person.

Fishing- Though this has been around for ages, and has been used by many RMT/botters NPCing their catch for years. Many people know about this, and I'm not going to go into an anti-bot crusade in this post about it.

However, SE really didn't help the inflation potential these bots or people can bring in per day when they released Hakuryu. These fish are top-end, and hard to catch, and catching one is hard with an Lu shang's fishing rod, and a bit easier with an Ebisu fishing rod (though bots can make this much much easier to catch mind you) and these fish NPC for 10,516 gil. Though there is a catch limit now, players (usually bots do this) can determine what is on the end due to the message recieved when they bite, and they can let go any other bite than from the Hakuryu, making sure than Hakuryu are the 200 fish they real in that day, netting them over 2 million gil per day, per bot.

Abyssea- Just throwing in these two in general as well. Abyssea gold chest items tend to npc for 1-7k a piece, and it doesn't take long for those NPC'd items to add up.

WoE- Though it costs 1k gil/entry now, it is quite easy to get 2-3x your investment per run in NPCables per run. This isn't a lot, but its making the entry fee useless.
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TLDR- Gilsinks have gone down, ways to NPC for gil have gone up, going down a bad route.