Activate Soulfire Grand Master by paying 2U/RU/R, causing you to put the next instant or sorcery card you cast into your hand instead of your graveyard as it resolves.
Cast an instant or sorcery spell by paying its mana cost, targeting Dockside Extortionist.
Orvar triggers, creating a token copy of Dockside Extortionist.
The Dockside Extortionist token enters the battlefield, creating a number of Treasure tokens equal to the number of artifacts and/or enchantments opponents control.
Resolve the instant or sorcery spell, returning it to your hand.
Activate any number of Treasure tokens by tapping and sacrificing them, adding 2U/RU/R plus enough mana to cast the instant or sorcery card.
Repeat.
Once you have infinite mana, you may target any permanents you control in step 2 to create infinite token copies of them.