Ads Don’t Fix Weak Math
Ads Don't Fix Weak Math: a practical framework for understanding paid advertising economics, contribution margin, acquisition cost, ROAS, and profitable growth.
A book in progress by Florian Coman
Ads Don’t Fix
Weak Math.
You can improve your ads and still lose money on every new customer. This book is about the numbers that decide whether paid growth can work—and what to change when they don’t.
Principles of paid ad economicsWritten for business owners and operators
SCALING ROAS
Ads
Don’t Fix
Weak Math.
Don’t Fix
Weak Math.
Principles of paid ad economics
Cover concept · not final artwork
01 / The idea
Advertising is a magnifier.
More traffic makes what’s already happening in your business happen more often. If each additional customer leaves too little money after costs, buying more customers exposes the problem faster.
This is the starting point of the book: look at the economics before changing the campaign. Work out what you can afford to pay for a customer, what you actually pay, and which assumptions have to hold for the difference to become profit.
“Ads don’t fix weak math. They expose it faster.”
02 / The acquisition chain
Follow the money from click to contribution.
Start with an ad budget. What it buys, what converts, and what each order leaves behind determine whether acquiring customers makes financial sense.
STARTING POINT
Ad budget
The amount you commit to acquiring customers. More budget increases volume; it does not repair weak economics.
CORE LEVER / TRAFFIC
Cost per click
How much you pay for a visit. This is the traffic cost that starts the calculation.
CORE LEVER / WEBSITE
Conversion rate
How many visits become orders. Traffic cost and conversion together determine acquisition cost.
CORE LEVER / ORDER
Average order value
How much revenue the acquired customer generates on that first order.
CORE LEVER / ECONOMICS
Contribution margin
What remains from that order after its variable costs, before paying for acquisition.
Optional fifth leverLifetime value
If customers buy again, their additional contribution may support a higher acquisition cost. That only helps when repeat purchasing is measured and the business can afford the payback time.
The four immediate levers are traffic cost, website conversion, average order value and contribution margin. Follow them in that order to locate the constraint; evaluate lifetime value separately where it applies.
03 / One small change
Same clicks. Very different outcome.
A campaign can look healthy until you connect its traffic cost with what each order actually contributes.
Move the conversion rate below. The click cost and order economics stay the same. Watch what happens to acquisition cost and the money left per new order.
Illustrative example. The €50 contribution per order assumes all non-ad variable costs have already been deducted; fixed overhead and taxes are excluded.
Illustrative order economics
Average order€100
Contribution before ads€50
Cost per click€1.00
Break-even CPA€50
Cost to acquire one order€50.00
Contribution after ads€0.00
At 2.0% conversion, 50 clicks produce one order. Those clicks cost €50. That uses up the order’s €50 contribution.
04 / Common mistakes
Where the diagnosis goes wrong.
The book looks at familiar advertising problems through the economics underneath them.
“ROAS is up, so we’re profitable.”
Revenue divided by ad spend says nothing about how much of that revenue survives product and operating costs.
“We just need better targeting.”
Targeting may help. First ask whether the business can pay the acquisition costs it is likely to face.
“Customers will buy again later.”
Future value matters when it is supported by real repeat behavior and the business can fund the wait.
“It works at this budget. Let’s double it.”
Higher spend can change reach, click cost, conversion and the mix of customers. Recheck the economics at the next level.
05 / The method
Find the constraint. Test the lever.
A diagnosis should lead to a decision. Each lever has a limit, a cost and an amount it must move to matter.
01 / Traffic costChange traffic mix, creative, placement or auction conditions.Ask: how much cheaper must a click become?
02 / Conversion rateFix the offer, landing experience, trust gaps or checkout friction.Ask: is the required website CVR plausible?
03 / Average order valueImprove bundles, pricing, order composition or upsells.Ask: does the change preserve margin and conversion?
04 / Contribution marginRevisit variable costs, fulfillment, discounts and product mix.Ask: what contribution remains on an actual order?
05 / Lifetime value (optional)Measure actual repeat contribution and payback before increasing allowable acquisition cost.Ask: when does the cash come back?
06 / Inside the book
A preview of the questions it tackles.
Selected themes from the manuscript. The chapter titles and final layout are still being edited.
Advertising is magnification
Why buying traffic accelerates the economics already present in the business.
Order value and margin
How much a first order contributes before the acquisition bill arrives.
Traffic cost and conversion
How the cost of a click and the website conversion rate determine the cost of one new customer.
Why ROAS misleads
What the familiar headline number leaves out, and which decisions that can distort.
When scaling breaks
Why profitable performance at one level of spend is not a promise about the next.
Use the numbers to decide
Realistic scenarios, break-even thresholds and changes that move the outcome.
The question behind every chapter
“What would have to be true for the next customer to be profitable?”
Put the thinking to work
Start with your numbers.
Go deeper with AdsMath
Get the €49 AdsMath Simulator and Decision Guide PDF to work through your own numbers and find your break-even points.
See the Simulator + Decision Guide ↗Get a deeper diagnosis
For a business-specific review of the model, the constraints and the decisions they point toward.
See the AdsMath Review ↗
