Why are Agent Shop prices much more expensive nowadays?

I, like many others are seeing a big price jump in items in the AH. Whats the cause of it, or are people just getting more greedy, or is there some logical reason behind it all?

Sigmetal event

Everybody trying to +9 means tons of people wanting UCH which means their prices rise. VC prices (and a few other dungeons) rose because they frequently drop UCH.
FCHH rose because people use it to increase chances of sucess when doing +8 and +9

First, I'm fairly certain I've seen higher prices than those we have now. Some of the contributors to price fluctuations that I can think of are:

The amount of items dropped overall in a given server during a particular timespan. If a given month shows a shortage of seal of darkness (sod) drops for whatever reason, you can expect prices to change accordingly.

The effect of events on the prices of items used or rewarded in said event. Some examples would include the socks in some of the winter events giving account binding dungeon keys such as sod, causing people to not need to buy as many during a given timespan, or the sigmetal event that allows people to sell uch at prices as high as they want so long as there is no source selling them cheaper consistently (which is why uch could go up to just under 1.5m).

The introduction of new items into the game. This effect can depend on the manner in which they are introduced. The new mergaheph ring, for example, brought a surge in epaulet of the undead (eod) prices that was much greater than had previously been seen.

Also keep in mind that when dungeon key prices are affected for whatever reason, the prices of items farmed from those dungeons will also be affected, and the reverse can also hold true. The only items that do not change prices very often, or at least not enough to be accurately measured, are very rare and coveted or very commonplace items.