I undercut almost every time I sell. Granted I don't do crafting or the like, if I get a hot item I look at the MB, see what it goes for an cut it by about 5-10%. Why? I didn't put any real effort to getting it, so me taking a 5% isn't anything big. Plus, when I look at the MB for a lot of stuff, there's a bunch of people selling the stuff at the same price. What is going to make random player-1 from picking my retainer over the other 29 who are selling?

Oh yeah, a price cut.

Even if I was doing a massive crafting/mining session I would still try to cut a small % off to make mine stand out more. It's basic economics - and it applies to in game too. If that makes me a jerk or someone who needs to be "regulated", so be it I guess.