See, this is something I've never grasped. Every time I've tried to learn the AH, and tried to track prices, even with the help of mods, I've never managed to turn a profit.
With every profession across my toons I think it's more of a hindrance than a help, as it is overwhelming. It helps in the long run for saving gold, where I can use all my professions to make stuff for myself, but I've tried making money off the AH by crafting things and people just undercut.
Example: There are always high end enchants up, quite often for just above the current cost of enchanting mats, meaning the sellers are not turning a reasonable profit, and to undercut would mean breaking even for me.
It's hard to tell which glyphs are in high demand, but the ones that seem like they should sell well; well, the market is flooded with them at 1-2g.
Gems are similar to glyphs. You could possibly make 2-5g on an epic gem cut that is in demand, but someone is likely to come along and simply undercut you and you end up with the gems back in your mailbox.
Haven't tried selling flasks and elixirs very often.
The only thing I can say is that if you want to make money off the AH, you will have to spend some time tweaking and adjusting your snatch variables, look for what is in demand, and post items on the weekends when more people are playing.
If you can't spare the time it takes to learn and stay up to date with item supply and demand, then making gold off people's instant gratification is going to be very tricky.
But I'd rather attempt to sell stuff than to go out and grind daily quests.
I keep plugging away at it, but there are too many people with each profession providing a service at little to no profit, that it means your timing has to be good as well as knowing when to buy and when to sell what.