FFXIAH
On this website, for one, you can check prices and ah histories and, basically everything AH related. It's also linked to Somepage when you look things up. I love this tool, I use it even while playing since it's faster to check than running to the AH.
Anyway, related to the 'depression' of ffxi. They posted a chart, using the data off each server, using sales, prices and so forth to give points to certian things. You can easily see the decline in the market.
It's pretty easy to figure out. Everyone wants to blame RMT for this decline, but in reality it is SE that did this, and they did it purposely. They would have the RMT round up billions of gil, then delete that gil. It was faster than hoping Chocobo prices, and Dynamis costs would delete gil. They do it every month now it seems when they ban accounts.
With that money being just removed from the server, with no way of it coming back into the economy, wether it be from people purchasing that gil, or from the RMT using it to gear up their characters (Which at least on my server, they do), it's not coming back now. With the RMT continually farming items we buy on the AH, collecting that gil, and SE continually deleting the accounts when they have the gil stashed. People are running out of money.
Thus, economic depressing that will never return to 'normal' per what it was the previous year. Basically, get used to prices dropping, people not being able to afford anything, and what you have being worth less.
Simply put, when it was at peak, it'd have (obviously) been almost worth it for anyone who invested in gear, to sell everything they have for gil, store the gil and stop p laying for 2-4 months. Come back to the game and rebuy everything, you'd have stock piles of gil to spend on low cost items.
Most of the gil on servers was duped, billions of gil didn't come from these piddly 1K quests and killing beastman, or using THF abilities. This changed the economy in one direction, now they're flipping it back. Sadly this kills every person who has been playing in the last year or more, as they most likely did invest gil into gear, buying high now it's worthless.