Why your own store beats a marketplace on the second order

Marketplaces win the first order. The buyer searched, compared, and picked a price. The second order is where an own store changes the arithmetic, because the customer is yours to reach without paying for the click again.

The second order is cheaper to earn

On a marketplace the repeat purchase still runs through the same fees and, often, the same ad. On your own store the repeat is a message and a link. The first order can cost more to win; the ones after it are where the margin sits.