Hey guys. I'm new to the forum and new to Facebook marketing so be nice 
I've been running this Facebook campaign on a 5k account I have for a couple weeks now. I got up to about 4k a day in spend running internationally and didn't want to increase the budgets anymore because I felt like my demo wasn't big enough so instead I expanded the offer into the US. I ran a test ad with a $400 budget and got some very nice looking 12 cent clicks! I was pretty excited so I fired up my 2nd account with the intention of putting this same ad on it and then scaling up. Much to my dismay, when I put the ad on the new account, suddenly my clicks were 24 cents! Same image, copy, bid, budget and targeting. Thinking that it might be a glitch, I canned the ad and ran it again the next day. same results! I tried yet again for a third day and nothign changed. Meanwhile, the original ad I created on the other account kept running at 12 cents. The CTR was almost double on the original account.
My Demo size was pretty big, like 5 million people. I used CPC bidding on both accounts and bid the same per click, running the ad on mobile only. Both Facebook accounts are running on separate IP addresses/computers. The only thing different besides obviously the Facebook accounts themselves was that I ran each account to a different landing page URL (with the same landing page though).
Does anybody have any idea what might cause this to happen? I am so confused and lost!!! 
My situation: Same ad, same account, vastly different results. Demo: 8 million
I can't understand Facebook anymore.
Complex ad delivery algorithms, variable audiences, ads sensitive to performance history in CPC mode, possibly some account-level differences that FB won't reveal. FB is complex cf. buying a banner at the top of a website.
If I wanted to scale something, I would just clone the campaign on the initial account.
I have experienced the exact same thing. Five of us were running a private offer (diet niche) with a $1k day spend, with the EXACT same image, text, targeted demo..everything. Unfortunately, our results were far from exact. Lucky for me, I was in the break-even category.....but after running it for a few weeks, trying to tweak and get the results of the two guys who were making $1k/day in profit, I moved on.
FB is the beast that cannot be tamed.