If there's one thing concerned students and clients want to know ...
It's why ads tend to "yo-yo" so much.
Some days your CPA is $20 and other days it's $100.
A lot goes into determining what your CPA will (likely) be for a day.
First - the "lighthouse" effect.
Facebook only has so many buyers (especially GOOD buyers) in its ecosystem.
And it only gives you access to that pool of A+++++ buyers on occasion - otherwise it would run out of them.
So it deliberately cycles you out of that great pool into decent but not the worst pools.
This is more about your market size and the number of folks who you're solving problems for than anything else.
Second - What others in your space (and beyond) are doing.
Remember that the ads marketplace is both a marketplace and a full-fledged ecosystem.
If your competitors go and launch 50 ads, the auction will certainly be impacted.
This means Facebook has to "rebalance" and "reprice" what it's charging in real time.
This is some of what GEM and Lattice is meant to accomplish.
What can you do about this? Study what others in your space are doing, and how the audience is reacting to it. If you notice trends emerging, test your variations and see if the algorithm latches on to it.
Third - Facebook just being Facebook.
Sometimes the engineers vibecode the latest changes and it TANKS.
The worst part is, there's very little you can do about it.
This is a legit phenomenon and it does stink - but there's not much we can do when that happens.
Each account varies.
Sometimes you ride the waves.
Sometimes you pause - it's hard to say what to do in each and every situation.
Over time the choppy waves settle and things go back to normal.
Overcorrecting, especially when it's Meta doing Meta things, tends to backfire badly.