Ill-Gotten Gains
The Copper will be gained in these cases:
- player has Copper in his buy rules and its buy conditions are met
- adding the Copper will increase this turn’s buying power
Trash and Discard priority number are set high enough to allow Developing, Remaking, Warehousing… this card.
Geronimoo's Dominion Simulator 
I put a note on the mint to say that the mint doesn’t gain extra iggs in preference to silver. The thief and pirate ship both trash copper in preference to an igg. This is a big loss for the thief. The complication is that the thief should trash an igg ahead of silver but a pirate should trash a silver ahead of an igg.
Ill-Gotten Gains rush/thief(Plr 2) plays Thief
… Ill-Gotten Gains rush(Plr 1) reveals [Copper, Ill-Gotten Gains]
… Ill-Gotten Gains rush(Plr 1) trashes a Copper
… Ill-Gotten Gains rush(Plr 1) discards Ill-Gotten Gains
Small point. A bot with igg, silver, silver, copper, duchy in hand will trash a copper when an opponent plays a bishop. This leaves the bot unable to buy a province.
Forget that. I can’t add up.