Re: Pathfinder - Poison
Instead, I imagine a better comparison would probably be like Ray of Enfeeblement. (1d6+1 per 2/levels against STR)
It requires an attack, has a save, etc. It doesn't have the risks of using poison, but it does require spell casting ability, or the ability to fake out the use of magic.
That brings up another option for a basic... simple poison would be something comparable to a Ray of Sickening. As I mentioned before...Sleep is an obvious one... it would only impact one person, unless you allowed it to be a gaseous poison released by throwing a vial.
Another idea for a cognitive poison would be something with an effect similar to Color spray, another first level spell. It could require wounding someone, or could be inhaled as above. I think I'd offer those adjacent the target square a +2 to the save, and/or consider their level one higher, or twice their actual level.
Lets actually take Touch of Fatigue... which is a cantrip. Actually, according to I think it is Skull and Shackles, some alcohol might be considered an ingested poison that creates a fatigued, or exhausted condition. Why not allow a poison/alchemical option for lower level adventurers.
You could probably actually control poison better by making getting specific poisons very difficult to find, and in limited quantity before supply being exhausted. You could however have certain regions have access to certain poisons at potentially, with good skills, reachable difficulty. Some poisons might be available given time, and premium payments made to boost your DC to acquire it.
It seems reasonable for poisons to potentially be priced around the price of a potion for a spell of similar effects. It generally shouldn't cost lest, save potentially, a sleep dose, might cost less if it can only affect one target, requires a chance of self-poisoning and requires a successful hit. Also, you could place expiration on poisons if you want to, making them become less potent, or useless after a specified time. Other options, as I mentioned, might include certain species having immunity or having a natural resistance. These quirks might be enough to insure people don't rely on it too much.
Potential quirks:
Immunity sensitive: After rolling any successful save vs. this poison, all subsequent checks for this poison are considered successful for 24 hours.
Occasional immunity: After rolling a natural 20 on any save vs. this poison. All subsequent saves for 24 hours are considered successful.
Progressive resistance: After rolling a natural 20 on any save vs. this poison, all subsequent saves vs. this poison are given a permanent +1 resistance bonus. The same occurs for rolls of a natural 1, but may be limited to occurring after the initial effect wears off. The benefits of multiple saves over time can stack, to a maximum of the character's level. (might rule that these resistance bonuses will not stack with Racial bonuses vs. Poison.)
But these quirks could help keep costs down and make poison use provide potential issues.