Cost per purchase is how much you’re spending on average in advertising to generate one purchase or transaction. This is essentially the same as cost per acquisition but the terminology is often used in e-commerce and retail contexts. If you spent $10,000 on Facebook ads and generated 100 purchases, your cost per purchase is $100. This metric needs to be evaluated against your average order value and profit margins to determine if your advertising is profitable. A $100 cost per purchase is great if your AOV is $300 with good margins, but terrible if your AOV is $80.
The E-Commerce Profitability Equation
In e-commerce, profitability comes down to the relationship between cost per purchase, average order value, and profit margin. You need your CPP to be significantly lower than your profit per order or you need backend monetization through repeat purchases to make the math work. A lot of e-commerce brands operate at break even or a slight loss on first purchase because they know customers will buy again and the lifetime value makes it profitable. This only works if you actually have good retention and repeat purchase rates. If you’re losing money on acquisition and customers don’t come back, you’re just burning cash.
Lowering CPP At Scale
Reducing cost per purchase while maintaining or increasing volume is the holy grail of e-commerce advertising. You do this through better creative that stops the scroll and drives clicks, better product pages that convert traffic at higher rates, strategic upsells and cross-sells that increase AOV, and audience segmentation so you’re showing different products to different customer types. You also need to be testing constantly because creative fatigues fast in e-commerce and what worked last month might bomb this month. The brands that dominate are the ones running dozens of creative tests every month and ruthlessly killing underperformers while scaling winners.