This is going to be a quick tip and based off of my experience in my gem market. Different markets will vary.
I tried to reset the Inferno Ruby prices on my server this weekend to 250 cut per gem. I bought a ton between 95-110 gold. Unfortunately there is one guy in the gem market who seems to deal only in red gems. He undercut all of my auctions down to 125 within minutes of coming online.
I was hoping that he would run out, but he appears to have a never ending supply of inferno rubies.
On the other hand, one of my competitors (the only one that I actually have converstations with) pretty much reset the orange and purple gem markets. Most cuts are going for more than inferno rubies are right now.
What I am saying is make sure that you know your market and competitors. You will make a lot more money in the long run. I will make a small profit on the 40k in inferno rubies that I bought, but it will take me probably a week to unload all of them.