Here are the reasons why:
– Text- heavy posts, especially memes, violate the 20% text rule, so you get disapproved or penalized.
– Some organic posts cannot be boosted– they have profanity, use Facebook’s brand the wrong way, or violate the ads TOS (like have a gun pointed towards you).
– You’ve exhausted the original audience, so your frequency is high when you a boost.
– You’re targeting the wrong audience– this is hard to diagnose.
– Your organic post wasn’t evergreen– perhaps for an event that expired.
You can see that the boosted part of this post got north of 10% engagement, which is excellent.
But we’re paying a $50 CPM– meaning $50 to reach just 1,000 people.
(Yes, the experts here will point out that impressions and reach aren’t exactly the same, but for the purposes of simple analysis, it’s good enough).
Even with a high base cost of traffic (CPM), the cost per engagement is good enough that I’m willing to let the boost live for a few months longer.