Estimate annual e-commerce GMV impact of 10% increase in delivery fees

You are a PM on a $10 Billion annual GMV on-demand delivery platform. Estimate the net financial impact on GMV and Platform Gross Margin if base customer delivery fees are increased by 10% (from $4.00 to $4.40).

Context

Increasing delivery fees increases per-order fee revenue but risks customer conversion churn due to price elasticity of demand.

Clarifying questions to ask first

What is the baseline order volume and average basket size? ($10B GMV, $50 AOV, 200M orders, $4.00 base delivery fee)
Is subscription/membership (free delivery tier) affected? (Non-members only; assume 50% of orders).

How to approach it

Deconstruct current baseline economics: $10B GMV / $50 Average Order Value (AOV) = 200 Million annual orders
Apply Price Elasticity of Demand for delivery surcharges (Elasticity ~ -0.4 to -0.6 for delivery fees)
Calculate Order Volume Churn: 10% fee hike × -0.5 elasticity = -5% order volume decline (Loss of 10M orders)
Synthesize Net Impact: GMV Loss (-$500M) vs Additional Fee Margin Revenue gained on remaining 190M orders

Framework: Net Financial Impact = (Lost Order Volume × Baseline GMV/Margin) vs (Retained Orders × Additional Fee Revenue)

Sample answer

Baseline: 100M non-member orders with $4.00 delivery fee = $400M fee revenue
10% fee increase to $4.40 (+40¢ per order)
Elasticity of -0.5 -> 10% price increase leads to 5% drop in non-member order volume (-5M orders)
GMV Impact: -5M orders × $50 AOV = -$250 Million GMV drop (-2.5% platform GMV)
Fee Revenue Impact: 95M remaining orders × $4.40 = $418M fee revenue (+18M net fee gain)

Loss of $250M GMV (-$37.5M lost merchant commission at 15% take rate) vs Gain of $18M delivery fees = Net platform gross profit change of -$19.5M unless offset by higher basket sizes

Executive estimate: GMV drops by -$250 Million (-2.5%); delivery fee revenue gains +$18 Million, but net platform commission profit declines by -$19.5 Million unless subscription conversion increases.

What interviewers look for

Baseline Unit Economics Modeling
Price Elasticity Assumption Justification
Volume Loss Calculation vs Margin Gain
Strategic Tradeoff Executive Synthesis