You are running a Facebook ads campaign for a new beauty product. The campaign cost is P50,000, it generated 1,000 installs, the install-to-purchase conversion rate is 5%, and the average order value is P800. What is the cost per paying customer, and would you recommend scaling this campaign? Show your math.
RoleDigital Marketing Associate
DifficultyMedium
TopicSales & Service
Asked at
Why This Is Asked
A small number of candidates have reported math and logic questions in Shopee marketing interviews, so this is worth practicing, though it is not confirmed as a universal part of the process.
General Approach
State the formula aloud, do the arithmetic clearly, then interpret the result in business terms. End with a clear yes/no on scaling and a one-sentence rationale.
General Answer
Cost per install equals P50,000 divided by 1,000 installs, or P50 per install. The number of paying customers equals 1,000 installs multiplied by a 5% conversion rate, or 50 paying customers. Cost per paying customer equals P50,000 divided by 50, or P1,000. Since the average order value is only P800, each paying customer generates P800 in revenue against a P1,000 acquisition cost, meaning the campaign is currently running at roughly a P200 loss per paying customer before even accounting for product cost of goods, shipping, or other overhead. Based on this alone, the recommendation would be not to scale the campaign as-is, since acquisition cost currently exceeds order value. Before scaling, it would be worth lowering the cost per install or improving the install-to-purchase conversion rate, checking whether repeat purchase behavior or customer lifetime value changes the payback picture beyond the first order, and confirming the actual margin on the P800 order rather than assuming the full amount is profit. If none of those change the underlying math, scaling the campaign would simply multiply the loss.
PH Interview Gotcha
Don't just say 'I will compute it and then decide' without showing the actual calculation. Walk through each step: installs x conversion = buyers, then cost / buyers = CPA. Then compare to AOV.
Sample STAR Answer▾
S
Situation
In a previous role, I was asked to evaluate a similar campaign for a subscription snack box where the CPA was too high to justify renewal.
T
Task
I needed to calculate the true cost per paying customer and decide whether to increase the daily budget or pause the campaign.
A
Action
I computed the number of paying customers: 1,000 installs times 5% conversion equals 50 buyers. Then cost per paying customer equals P50,000 divided by 50, which is P1,000 per customer. Since the average order value is only P800, the campaign loses P200 per transaction before overhead. Instead of scaling, I recommended pausing the campaign and shifting budget to a retargeting funnel for users who installed but did not purchase.
R
Result
The retargeting campaign dropped the cost per paying customer to P600, making the campaign profitable at a 25% margin. The client approved an additional P30,000 budget for retargeting.
Key Takeaway
Never scale a campaign without first verifying that the unit economics are positive.
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