If you play retail wow on US or Oceanic servers you may have noticed a big increase on prices. e.g:
Linen Cloth: was about 15-20s per stack a month ago. Now some are sold for 70s-1g a stack
Small Radiant Shards: was around 50-75s for 1 about 3 months ago. Now selling for 5-6g and more on some servers!
Most mats have increased in price by between 1g-10g (depending on the rarity). Some people are beginning to blame "gold farmers." These players lvl themselves up to a lvl that is comfortable for them and go and constantly kill npc's that drop a reasonable amount of gold. Doing this is making it hard for other people to make gold.
Another thing that people are beginning to blame is the simple matter of greed. One day some guy for no reason sells something thats say 20s and sells it for around 40s. Other players notice this and then they begin to do the same. In no time at all prices have increase dramatically.
Blizz has also noticed (as posted in there forums) that players are also beginning to receive large amounts of gold in the mail. These are probably from the so called "WoW gold sellers."
I just made a character on the Oceanic realm Frostmourne (due to my cuz has a lvl 70 night elf hunter). I made him an engineer and because I got gold off my cuz I mostly bought the mats from the AH (Auction House). I went away for about 2 weeks and when I got back and decided to lvl his engineering up, I was so surprised as to how much the prices had gone up. A simple bronze bar went from an average of 1g 50s to an average of 4g 75s!
So face it prices are probably going to go up even more and if they haven't on the realm you play on then give it a few weeks and they will probably go up as well. And if they dont well then consider yourself lucky.