Potion brewers need a union! They don't make any profit at all on their potions, not even so much as a copper.
The rules say: "The costs for materials and ingredients are subsumed in the cost for brewing the potion: 25 gp × the level of the spell × the level of the caster." And there is a table laying out the numbers.
Elsewhere, the rules say: "The price of a potion is equal to the level of the spell × the creator's caster level × 50 gp." And again there is a table laying out the numbers.
All well and good! Except the numbers are identical in both tables.
The table for prices says it's 50 gp to buy a finished potion of Cure Light Wounds. Caster level 1 x Spell level 1 x 50 = 50. Correct!
The table for costs says it's 50 gp to buy the ingredients for the same potion. Caster Level 1 x Spell Level 1 x 25 = ... 50 gp? Bzzt.