There are certain abilities that let you get more out of poisons. A few alchemist discoveries, and maybe a feat or two. Do a search on the srd or prd for poison and you'll find most of them.
Thanks guys, I was assuming that with a vial of poison I'd get a few blow dart applications out of it.
The character who's going to be using it is an alchemist but hasn't taken that discovery yet. Guess it will be worth it to buy the materials and spend a little time crafting it.