Right now the prices of several items don’t justify auctioning them.
It’s possible to start bank alts (to stockpile for AQ). However, with the price of bag slots in the bank, either you need very many alts, or high profits. The last bag is 100 gold, even if you get a 20 slot bag, you need a 5 gold profit per stack to come even. (A bit more - you had to obtain a bag, too. Crafted? Could have saved the cloth to sell at the inflated price.)
With Auctioneer I made a slight improvement on my economics, but the AH price of most materials I come across floats between the vendor price (often just +1 copper) and the 50% extra. The only single exception I found so far: Elemental Fire. That goes for 2.5 gold. Thus, vendoring everything is almost a viable strategy, considering you don’t have to dedicate bag slots and return to the AH every so often.
The story turns around when you don’t care about gold anymore and invest for the fun of flipping, or making alt life easier. Like I did get myself a guild bank. Or, when we get to WLK and low level mats sell for about a gold apiece. Either way, you don’t fill your bank with Gate materials right now - you keep using the storage to make money in the meanwhile, so that the storage cost mentioned above gets refunded.