Ok, I think I understand how it works, I'm mostly here to check if I got it all right.
a) DC for the Craft (Alchemy) check is 5+CL of the potion
b) "Base Price" which is often quoted is the market price, and not the cost I have to pay (which is half that)
c) I need to spend a prepared spell/spellslot to make the potion
d) If I don't want to spend that, or if I don't have the spell prepared, or don't know it, or if it's not even on my classes spelllist, I can still make the potion, but the DC increases by 5? (I'm not sure about this part, but that's how I read it)
e) Just to make sure: A wizard trying to make a CLW potion with CL 1, has to hit a DC of 11?
f) Even if a potion only takes two hours to make (250gp or less), I can only make a single one per day?
Looks good. Note that potions are magic items, so Spellcraft should work IIRC for the skill check, not just Craft (alchemy).
Yes, I noticed that too, after I was done with the post, and so I did some math.
Assume a witch with Int 20, max rank in Spellcraft:
She'll have Level+3 (class-skill)+5 (int) = level+8 ranks in Spellcraft
DC for a potion that you don't have the spell for is, assuming its made at max CL:
5+5 (no spell)+Level = Level+10
So basicly on a roll of 2 I succeed. Get a magic item to boost Int by +2 and it won't even fail on a 1.
So really seems like Craft (Alchemy) and the +4 bonus from Cauldron hex is pretty useless there.
(unless I did something wrong here or didn't consider something)