RP Servers will always act differently to the others. Whether it's in general grammer, or how the Auction House runs, they're made with different mindsets in... well, mind.
Here's a recent example from myself. I bought this Swiftsteel Shoulders pattern on the Auction House for 525 gold. It's a Bind on Equip pattern from the Burning Crusade, and has little to no value in the level 80 scene. Yet, get this...
It looks awesome.
That's it. 525 gold into someone elses pocket for something that looks good. It's not something I make a habit of (i've been running Black Temple for it for a while now), but I don't like to be frugal in a Video Game. I leave that for the real world.
You won't find this mentality on any other type of server. People buy things that look good on Argent Dawn, driving said things prices up to bizarre levels. It also keeps old world materials high in price, as you need to craft half of these pretty things themselves. Is this a good economy? One built on vanity? Who knows, but it works. Sure Northrend materials are still worth something, but unless it feels good in the mirror it won't last long.