For all the tailors out there, as MoP comes out many folks will be rerolling a monk. With a new toons comes the responsibility to give it bags. I can see that there will be a spike in demand for bags. I will speak out all the different bags that can be used by many different groups of people in azeroth. I will try to go over on how to market all the new banks to all segments of WoW society in every sociecomical class from rich to poor. This this the investment is diversified.
Netherweave for the poor
Netherweave bags are cheap to produce and the most inexpensive bags on the AH. This is the perfect bag for all the very poor people whom can't afford anything better. And yes there are a huge population of gold poor people in WoW. This segment has great difficulty being able to afford things. This product targets the lower class of world of warcraft. You won't make as much per bag as the other classes but if you sell huge volumes you should be able to make gold even out of the poorest segment of WoW society.
Frostweave for working class
The next level is frostweave bags, people whom can afford these bags, but can't afford anything better. This group can usually afford the very basics of things in azeroth. This class of bags will cater to the lower middle class of world of warcraft. You have the luxury of being able to afford a bag better than those used by the lower class.
Embersilk for the middle class
The next level is embersilk bags, its for people whom have more gold than the lower class, and the lower middle class. This is the bag that caters to the middle class members of the WoW society. They can typically afford many things in azeroth, and am considered well off. You should be able to make a decent amount of gold selling to this class of WoW players.
Illusionary for the upper middle class
Higher up is the illusionary bag, this bag is for people whom have a fairly large amount of disposable income laying around. So I would say this bag will cater to the upper middle class. Those people can afford many luxury items in azeroth as well. You will not sell many of these since the upper middle class in WoW is a pretty small number. But each bag should be more profitable than the other bags that are produced.
MoP bags for the super rich
MoP bags: for those people whom are extremely wealthy, ie part of the upper class, they can afford whatever luxuries they want, consume the finest luxuries out there that many the folks in azeroth can't afford. If you happen to power lvl tailoring before anyone else and sells those high priced bigger slot MoP bags, the extremely rich would be able to afford those bags.
Profession only specific bags
Other misc bags: there are many other profession only bags/toolboxes with many slots: leatherworking, inscription, mining, herbalism, enchanting, jewelcrafting, fishing. You can only put profession only items in those bags, but they are cheaper than the general purpose bags. There might be a market for folks whom use those bags when they reroll a monk and pick a specific profession. I profession only bag helps save bag space if they are doing professions.