Success rate isn't random, it's a certian percentage modified by your companions affection and "natural" crafting bonus. I honestly don't know the rate at the moment, but since I generally craft an augmented piece within 6 tries, (My one odd 15 attempts is by far my worst, and about the 10th augmented thing I've tried for), I will use 1/6 for this example.
Ok, fine. To be completely accurate it's a weighted random, I guess I didn't think I really needed to specify weighted since most "randoms" in games are weighted randoms, and this one obviously is. (which actually makes the odds of "infinite" failure higher.)
If my chance is 1/6, I could charge 12x's the materials cost for one. That gives me 12 tries before I start losing profits.
In 12 tries (1/6 x 12/1 = 12/6 = 2) probability wise I should have made 2. Thus I profit.
So your statement is true there is "No way to charge a flat rate and always profit" but the probability you would lose money is low, and the amount of customers you will get from decent fees + uncomplicated transactions should make up for any once in awhile losses.
<.< For your flat rate, I'd just do a little research into the probability, then stack it in your favor within reason.
Which is pretty much what I was saying. I agree with the flat rate, hence my price of 10x CoM (though I'd put the odds closer to 1:5, and thus my figure of 10x CoM.) I'm just nitpicking that due to how random works (includeing weighted random), it is impossible to cover the "worst case scenario" as that would be infinite failures.