In the Secret History of Seaside, the blurb for Cutpurse begins:
This started out as "Cards cost $1 less this turn, then $1 more until your next turn." That doesn't have the same timing as the other duration cards - it goes away at the end of the previous player's turn, rather than at the end of your turn. The developers didn't like that.
Inspired by this idea and appreciative of the logistical dilemma, my brother managed to create a card that has this effect without the inconsistency:
Inflation
$5 - Action/Duration
+$3. Place on token on the Inflation mat. While there are tokens on the Inflation mat, all cards (including cards in players' hands) cost +($) equal to the number of tokens on the Inflation mat. At the start of your next turn, remove one token from the Inflation mat.
(Note: The +$3 is really only a net gain of +$2, and worse if you use multiple buys. It's also not labelled an "Attack" card due to the rules weirdness it would cause with Reactions.)
The idea is that, like Trade Route, you only have one shared mat amongst all the players. Using the tokens on the mat, rather than simply counting the number of Inflation cards out, allows the duration of the effect to last until the beginning of the player's next turn, rather than the end of it, while the card itself still gets to follow the rules of all the other duration cards. (Haven has a similar quality.)
After a few playtest games (during which we discovered the card should give +$3 instead of +$2 to make it sufficiently worthwhile to play, as then it feels more like the standard Mountebank/Militia/Cutpurse attack-with-a-terminal-silver card), we were both quite pleased with how it played.
A potential problem is that using TR/KC on it, or playing multiples with Villages, can really slam an opponent's next turn. We were expecting that problem, but even in a kingdom where we deliberately included lots of possibilities for playing multiples, it still didn't feel that bad -- certainly not as bad as the brutal punishment that chaining Torturers or Mountebanks will do.