Mind Melt sometimes sells decently depending on supply and demand, and I've also been paid for doing some poison combines for other quests that require them. (I had an enchanter pay me 1k for 2 poison combines for a quest that she had gotten the components for - she had even picked up a mortar & pestle for me, but I always have my collapsed set on me)

Otherwise, you'd only make money selling poisons to other rogues, because they're the only ones who are going to be able to use them.

However, you might still be able to make some money off of players by working up your Pottery skill in tandem with your Make Poison skills. (sealed poison vial taking you to 188 - unfired casserole dishes taking you to 199... I haven't progressed past that as my .sig shows)