Here's an illustration with made-up numbers. You sell a $60 product that costs $18 to make and run it on two channels.
On Channel A, a paid social campaign sending shoppers to your own store, you spend $15 in ads per order. That's a 4.0 return on ad spend. Shipping runs $7, payment processing about $2, the average discount code takes off $5 and returns average $3 per order. You keep $9.96 on each order.
On Channel B, a social marketplace, you spend $12 in ads per order. That's a 5.0 return on ad spend, which looks better. But the platform takes a $3.60 fee, creators earn $9 in affiliate commission, platform-funded coupons cost you $10, shipping is still $7 and returns run higher at $5 per order. Add the $18 in product cost and $12 in ads and you lose $4.60 on every order.
Run 1,000 orders a month through each. Channel A earns about $9,960. Channel B loses about $4,600. Ranked by return on ad spend, Channel B wins. Ranked by which channel you keep, it's the one to cut.
We've covered why that happens at the brand level in our posts on marketing efficiency and your P&L and on contribution margin. The channel view takes the same logic one step further, because the break-even point moves from one channel to the next.