06/19/2026
A seller showed me his account last week.
ACoS was 14%. Clean. Consistent. He was proud of it.
But his market share had dropped 18% over the same 90 days.
His competitor was running at 38% ACoS and quietly taking every customer he was turning away.
This is one of the most expensive misunderstandings in Amazon PPC right now.
Low ACoS does not mean your business is growing. It often means you have pulled back so much that you have handed the market to someone willing to invest more aggressively.
ACoS measures how efficiently you spent. It says nothing about whether you spent enough.
The seller who runs at 38% ACoS and breaks even on the first order but retains that customer for 12 months wins. The seller who runs at 14% ACoS and never acquires that customer loses. Quietly. Slowly. And usually without realizing it until the organic ranking is gone.
What actually tells you if your PPC is working:
TACoS trending down over 60 to 90 days means your paid spend is building organic velocity. That is the goal.
Market share holding or growing inside your category means your visibility strategy is working even if individual campaign ACoS looks high.
New to brand customer percentage tells you if you are acquiring new buyers or just converting the same audience repeatedly.
The obsession with low ACoS is understandable. It feels like control. But control without growth is just managed decline.
The question is not whether your ACoS is low. The question is whether your business is larger than it was 90 days ago.
If the answer is no, the ACoS number does not matter.
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**FACEBOOK POST:**
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A seller showed me his Amazon account last week.
ACoS was 14%. He was proud of it.
His market share had dropped 18% over the same 90 days.
His competitor was running at 38% ACoS and taking every customer he turned away.
This is the most expensive misunderstanding in Amazon PPC right now.
Low ACoS does not mean your business is growing. It often means you pulled back so far that you handed the market to someone willing to invest more.
What to track instead:
🟢 TACoS trending down over 60 to 90 days means your ads are building organic growth
🟢 Market share holding or growing means your visibility is working
🟢 New to brand percentage tells you if you are actually acquiring new customers
The question is never whether your ACoS is low.
The question is whether your business is larger than it was 90 days ago.
If the answer is no, the ACoS number does not matter.
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**INSTAGRAM POST:**
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ACoS 14%. Business shrinking. 👇
Saw this exact account last week.
Clean ACoS. Proud seller.
Market share down 18% in 90 days.
Competitor running 38% ACoS.
Acquiring every customer this seller turned away.
Low ACoS is not the goal.
Growth is the goal.
What actually matters:
✅ TACoS dropping over 60 to 90 days
✅ Market share holding or growing
✅ New to brand customers increasing
ACoS measures efficiency.
It does not measure whether you spent enough.
A business with 14% ACoS and shrinking sales is losing.
A business with 38% ACoS and growing market share is winning.
Know the difference.
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