The Industry Standard
Anyone who makes a money with the tailoring profession probably has delved into the Netherweave Bag market. These trustworthy sellers do sell in high volumes, are not expensive to craft, provide a decent return on investment, and will never run you into overstock issues. They are the preferred choice of most players who are increasing the bag space of alts or stocking up extra bank tabs. When you compare your options, these are not the smartest purchase for leveling alts.
Better Choices For Alts
Both Traveler's Backpack and Mooncloth Bag are better options for alternate characters (alts). The biggest disadvantage of using Netherweave Bags is that they Bind-On-Equip. So once the new alt adds them to his bank or equips them into his / her bag slots, they become bound to that single character. If this alt later purchases better bags for even more space, these are often vendored for a fraction of the original cost, since they cannot be used on any other characters. Neither the Traveler's Backpack or the Mooncloth Bags are bound upon use. They have the same 16 slot space allowance, but allow the cost efficient player to utilize them on multiple characters. If they get replaced by larger bags, the option still exists of sending them to another alt for use witout having to purchase more bags for the new alt. The other option that exists is a quick trip to the auction house for resale. Think of these bags more like you are renting them, instead of buying them outright, just to be vendored after they are outgrown.
How Are They Obtained?
Mooncloth Bags are crafted by tailorings that have learned the Pattern: Mooncloth Bag. Both Traveler's Backpacks and the pattern for the Mooncloth Bags are rare vanilla world drops. Be sure to grab this pattern, if you find it posted for a good price on the auction house. Add Felcloth to your snatch list. Nowadays you can find it pretty cheap as most people just dump it to the auction house due to its limited usage in useful items these days. Some buyers are aware of the benefits of using these 2 bags instead of the standard Netherweave Bags. I often sells Mooncloth Bags and Traveler's Backpacks for 16-25g each, which is much higher than the usual sale price of the Netherweave Bags. Watch for Traveler's Backpacks that are underpriced and snatch them up to flip for a profit.