Writing Invitation Rewards

Ive done about 20 or so Writhing Invitations this league and have never seen drops other than the standard stuff you see from a map monster. Does the infinite hunger actually drop anything?

someone was buying mine for 30c each so he must drop something

They can be decent but absolutely require certain atlas passives:

Regurgitated Relics (chance to dupe eldrith currency)
Conquered Conquerors (chance to drop conqueror maps)
Height of Hubris (100% incr. modifiers on invitations)

You also want to alch and preferably vaal them for very high quantity and favour a map that is in high demand when comes to conqueror maps. Influenced crimson temples were being traded for up to 100c/map fairly early in the league and bulk selling eldrith currency is quite insane.