Is paid advertising still worth it for ecommerce?

Worth it as an accelerator, ruinous as a foundation. Advertising into a business with repeat customers compounds; advertising into one without them is a subscription.

The reasoning

The number that decides it is the ratio of lifetime gross profit to acquisition cost. Above three it is a good use of money; near one you are working for the platform.

What most people get wrong

Attribution is harder than the dashboards suggest. A customer sees six things and the last one takes the credit.

The cheapest customer is the one you already have, and most budgets are spent as though that were untrue.

A channel that works at small spend often stops working at large spend, because the cheap audience runs out first.

How an app changes it

Push notifications sit on the owned side of that line, which is the whole commercial argument for an app.