So heres a little case study I've come up with and I hope it helps someone. This is all based on the general marketing rule of 1/10. Meaning 1 out of every ten will act. Its not science but its a safe way to measure expected results. OK, so I'd collected about 40k member emails from facebook. These were all passionate/active users in the niche. These FB emails were to be used for laser targeting ads for selling teespring shirts. I'm sure you've probably seen some posts already on how some have used this edge to their advantage but more often you will see posts about many who have failed. So, how do you know if you'll pass or fail. Lets break it down: Of those 40k users I had collected, FB only accepted 32k of them into a custom audience. Now if 1 in every 10 people will click on the ad, that's 3200 clicks. Sounds good but not so fast. We have to break it down once more. Of those 3200 click, 1 in 10 will convert into a sale. 320 If your markup is $3 per sale, you got $960. Not bad for about 2-3 hours of work! But here comes the expenses. Remember 3200 people clicked and even though only 1/10 of them bought, you still have to pay for the rest. 3200 X .30 (per click) = $960 You just broke even! Not as easy as it sounded right? Now of course $3 profit and .30 per click are just hypothetical numbers but they are about average. It's not as "get rich quick" as it seems but here are some things you can do to offset the break-even and actually turn profit but it will require a little more work. Make damn sure the audience you are laser targeting are highly active/passionate. This will in turn increase your ratio to maybe 2-3:10. By this example, you can figure that any audience that's below 30k will likely not be worth your time. Find ways to increase the profit and/or lower the CPA. The .30 is just an example and you'll probably be able to get a little lower but you should still plug in this ez formula to get a rough idea and find your break-even. Do not calculate by the number of addresses/ids you've collected but instead use the number of them FB accepts upon creating your custom audience. Focus on converting landing pages. IMPO: teesprings "minimum order" displayed to the customer is a BIG buzz kill, but hey, to each their own. I would recommend actually putting in a little more effort/expense in making your own landing page. In summary: (amount of accepted FB audience) / 10 = A (action) A / 10 = B (bought) B X P (profit per sale) = R (total revenue) C (CPA) X A = E (expenses) R - E = Profit Again, this is just a bit of safe business sense. It's not down to a science but it can be used to get an idea of what you're getting into. If you come out to a break-even, its probably good as long as you are certain that your custom audience is highly active/passionate in their niche and you put a little more effort into having landing pages that are geared to convert. Best of Luck To All. Hope this helps!