I do this all the time, though not on purpose. On my server, for instance, I like to sell Desh at 50 creds each in stacks of five, which is at 250c. But lots of people on my server seem to think Desh is worth prices like 200c each, and try to sell them in stacks of three. So, while leveling a toon with strictly Gathering Crew Skills, I'll pick up somewhere between 200-300 pieces of something like Bronzium and sell stacks of five for 500c, when everyone else is trying to sell stacks of three for 1500c. Best part is, I have two Gathering toons doing the same thing, so I can list double the amount what SWTOR limits to one character and make craptons of money. I take pleasure in filling in pages and pages of material, I like to imagine I'm Mr. Burns or Scrooge McDuck
Personally, I have no idea who the hell is buying my stuff anyway, considering the people that actually need it can pick it up off the ground for free. Maybe it's the guys trying to gouge people.
Scavenging and Arch materials are my biggest sellers, followed closely by Underworld Trading.
LOL, your second point first. I have to agree and can't figure out who is buying desh and silica and the like. I have on occasion bought a ton of low level mats when I was power leveling a crafting skill simply because it is chaaper (time = money) and easier to do so than send out a 50 to gather the stuff, so the answer may lie with people doing similar things.
I was not thinking of low level mats in my post - the ones that (like the desh, silica, green goo, and so on) are so abundant that you end up constantly filling up your bags as you move around. I usually deal in the higher level stuff that cannot be gathered in large amounts, if at all, as you move around the worlds. The basic source is arch, bio or scavaging missions. I was also not talking about pricing high enough to sell one or two stacks and then retire on Alderaan after buying an estate on the river. Most of the higher level mats trade within a discernable range. It is not hard to get a feel for what the pricing should be over a short period of time. I had in mind the higher level, rarer, and more expensive stuff. If there is a page or two of listings most of which are priced within the normal trading range and someone comes on and lists a page or two at a few credits lower than the lowest auction, then everyone else is dead for the time of their listings.
I think that there is a difference in trying to dump the glut of lower level stuff at any price possible and trying to capture all sales of a specific item at the cost of others.
PS - As an aside, I think that I am seeing sales of mats (especially at the higher levels) slow down and am starting to wonder if the amount of craftng going on is .essening. Is anyone else noticing this or am I looking at a blip in my own experience on my server?