A high CPM on its own is not a problem. You are buying attention, and expensive attention that converts beats cheap attention that does not. The question worth answering is whether your CPM rose because the auction changed, because your audience is too small, or because your creative stopped earning attention. Those have three different fixes and only one of them is a settings change.
First, check whether it is you or the calendar
CPMs move seasonally and they move hard. The run into Black Friday and December lifts prices across the whole market, and a CPM that doubled in November has told you nothing about your account. Compare against the same weeks last year rather than against last month, and compare against a second account or a second market if you have one. If everything moved, it was the market.
Second, check the audience size
A narrow audience gets expensive quickly, because the same people see the ad repeatedly and Meta has to bid harder for each additional impression. Frequency is the tell. If frequency is climbing week over week inside a single ad set, the audience is too small for the budget you are putting through it, and the answer is a broader audience rather than a lower bid.
Frequency climbing inside one ad set is the clearest signal that the audience, not the creative, is the constraint.
Third, check whether the creative is still earning its place
Meta prices attention partly on how people respond, so an ad that people scroll past gets more expensive to serve. That is why a fatigued creative shows up as a rising CPM before it shows up as a falling return. Look at how long the current top ads have been running and what the click through rate did over that window. A CTR sliding while CPM rises is fatigue, and no bid setting fixes it.
What fixes it is new creative, and specifically a different idea rather than a different crop of the same idea. On Curated Chrome we ran Meta for seventeen months against €48 242 of spend, and the pattern held throughout: the winning ads were replaced by new concepts, not by variants.
Fourth, check what you are optimising for
An ad set optimising for a rare event asks Meta to find a small group of people, which is expensive by construction. If purchases are thin, optimising for purchases at a low budget prices every impression as though it were precious. Sometimes the honest answer is that the budget cannot support the event you are optimising for, and moving up the funnel temporarily costs less than paying for precision you cannot fill.
What CPM does not tell you
Nothing about profit. An account can halve its CPM and lose money, because the cheapest attention available is usually the least interested. Judge on cost per purchase and on what the store actually took, not on the price of a thousand impressions. If those two disagree, the disagreement is the finding, and it is usually a measurement problem first.
What we do with it
We read CPM next to frequency, CTR and the store's own revenue before calling it high, and we advise on the creative direction rather than producing the files. How the channel runs is on the Meta ads page.