DominionStrategy Wiki
Manufacture Action 5$ ? 6$ ?Skip your buy phase this turn.For each other unique card you've played this turn, you may gain a copy of it.
Maybe "up to 4" will nerf it a bit, so you can get your Villages or Smitties, but not start getting Wharves or Torturers or Margrave or Goons. It may make those engines built around cheap pieces (like FV + Watchtower) really fast.
The idea is to be able to buy only engine parts without actually getting vps/ending the game. Though it can end the game by excessive piling.