I think that you are speaking about ability damage. Ability drain is not curable with lesser restoration.
Lesser restoration can be used while target is still taking ongoing ability damage from affliction - it will heal 1d4 points of ability damage from those already suffered but it wont prevent damage inflicted by the effect later (unless it is some sort of Constitution bleed - in that case GM *could* rule that healing Constitution damage stops bleeding but it would be houserule - bleeds are stoped with hit point healing normally).
At significant cost from the wand yes. I don't mind this since you are still burning resources -- you are simply being a bit more proactive than you otherwise could be. Curing the poison would probably save more money and effort in the long run.
I'm fond of the spell delay poison. Delay the effects and cure them after the battle. Saves the costs of lesser restoration and keeps you fighting when you need to. Once you have time you can sit down and handle the poison with a heal skill check. Since delay poison lasts a very long time you can get a lot of mileage out of a single casting.
Delay Poison with the Extended spell feat is nice.
6th level caster extended delay poison = 12 hour duration.
12th level caster extended delay poison = 24 hour duration.
Until you got affected by multiple poisons at the same time and they all go off at the same time when delay poison ends. If they are different poisons they will hit all at the same time (and while RAW it is not specified I would rule that treat poison Heal use applies to specific poison not all affecting the target at once). If they are same poison... Well, extra doses increase save DC and duration.
Still lesser restoration can be life saver if you are out of delays and the healing from it can reduce total Constitution damage inflicted by poison to less than Constitution score.
Delay Poison with the Extended spell feat is nice.
6th level caster extended delay poison = 12 hour duration.
12th level caster extended delay poison = 24 hour duration.
The idea is, delay the poison, until you back to town, and get it neutralized. Or delay it long enough, to relearn your spell, so you can neutralize it yourself.
I just imagined assassins guild that hits with lots of cheap poisons to stack doses and then their spellcaster 'nukes' poison victim with dispel magic just to get rid of that pesky delay poison. Nahnhanha.
EDIT: missing 'imagined' verb added.
Hehehe, well that is one way to do it.