Say you run a gift card scam.
Victim buys $100 in gift cards and provides you codes.
You sell the $100 gift cards on a marketplace for $75.
A completely unrelated person buys the gift cards for $75 from you.
That unrelated person is satisfied, they got $100 for $75. They got a deal. You got $75 from a happy customer.
The loser is the person spending $100 in gift cards.
Other scams require you send money to a domestic “mule”, who then sends the money along not realizing it.