Esse é o excelente conto de William Tenn, " Ponte Betelgeuse " . É apenas uma correspondência ponto a ponto com a descrição.
Termina praticamente como você se lembra:
Here we are. Explain the situation to them, Alvarez, just the way I told it to you, but with all the knee-bending and doubletalk that a transplanted Brazilian with twelve years’ Oriental trading experience can put into it. You’re the man to do it—I can’t talk like that. It’s the only language those decadent slugs understand, so it’s the only way we can talk to them. So talk to them, these slimy snails, these oysters on the quarter shell, these smart-alecky slugs. Don’t forget to mention to them that the supply of radioactives they got from us won’t last forever. Get that down in fine detail.
Then stress the fact that we’ve got artificial radioactives, and that they’ve got some things we know we want and lots of other things we mean to find out about.
Tell them, Alvarez, that we’ve come to collect tolls on that Brooklyn Bridge they sold us.