How is the value of reciprocity displayed in the story that Demodocus(the bard) tells the Phaeacians?

I'm not quite sure where you are here but I'll guess Book 8. Demodokos sings about a tryst between Ares and Aphrodite, which ended when the cuckolded Hephaistos forged chains and snared them when they went to bed together. He then invited the other gods to witness the adulterers caught in the act. That's kind of reciprocity!