Crafting a Batch of something

[Splendor]

I haven't seen any rules for creating batches of alchemical items.
Are there any?

I was thinking something along the line of +5 DC and you create two of the item in the same amount of time. Base material costs is doubled.

Alchemical Sleep gas in the Realms is 25gp and a DC of 25 to make
So to make two alchemical sleep gas at the same time is DC 30 with a material cost of 16.67gp.

Time to make 1: 250sp / (25DC*25check)=.4 weeks
Time to make 2: 500sp / (30DC*30check)=.56weeks

Doesn't seem over powered to me.... Any comments?

[SowZ]

Base material costs won't actually double if the player is smart, though, since purchasing things in bulk is cheaper then if you buy things one at a time.

[Geigan]

Personally I'd just add the costs of them all together. Make your craft check and see how much you get done in sp, then divide by the standard 1/3 cost of the item you're trying to create and that's how much you get done this week. I'd rather not waste so many in character weeks on making simple items(though to be fair an alchemist can do a lot depending on what sources they have available). Your idea doesn't seem OP to me but I'd say my opinions are bit skewed.