Dud Turn Event - $8
Once per game: When you buy this, when each other player takes their next turn, they cannot can't buy cards.
It's once per game. You buy it, then your opponent buys it, and then you can't do anything and then it's your opponent's regular turn.
In that scenario, Dud Turn is really just an $8
Mission that forces* your opponent to also get an $8 Mission. (* Well, makes doing so the best available option, most likely.)
Hm, I guess Dud Turn hits your opponent the hardest when your opponent has the largest expected (buy-oriented) payload, i.e. when they're most likely to retaliate, in which case it's just trading Mission turns. Could you use it to your advantage in some other circumstance?
If they retaliate, you're trading Mission turns. That benefits the player with the largest (expected) non-buy payload—so gainers, attacks, maybe traveler upgrades.
If they can't (or don't) retaliate, your benefit on your turn is your full payload, minus the $8 spent on Dud, plus the non-buy payload you have over your opponent. Either that's close to nothing, or your decks differ greatly in payload.
For example, if you have $16/2 and get Dud/Province and they don't hit $8, your buy of Dud maybe stole a Duchy from them? At the expense of them buying Dud later and stealing two Provinces from you, I think. And if they hit $8 and retaliated, you stole a Province but they stole two from you.
So I guess in the case of asymmetric payload, a Dud Turn exchange on net harms the player with the highest (buy-focused) payload. The poor get richer. Good in Big Money.
Cool. Still, it belongs in RBCI