In The Piano (1993), Ada and Baine have a conversation like this:
Baine: How many would that be?
Baine: Yes. Ten keys.
And then both make love with each other.
What is the meaning of this conversation before making love?
Ada buys back the piano one key at a time by playing for him. Making love to him counts for ten times playing for him. At this point the relation between Ada and Baine is highly asymmetric: Baine desires Ada, Ada desires her piano. Only later does Ada fall in love with Baine.