Here's an idea I was mulling over in my head:
Inflation--Action, cost $2
+2 cards
Trash this card.
Place an inflation token on top of a Kingdom Card pile.
---
For each inflation token on a pile, that card's cost is increased by 1.
...and its natural complement:
Surplus--Action, cost $2
+1 buy
Trash this card
Place a surplus token on top of a Supply pile.
---
For each surplus token on a pile, that card's cost is reduced by 1 (but not to less than 0).
Some notes:
--I'm not sure if ideas like this have been discussed before; I tried a search but if there's already an existing topic please let me know.
--I know these are very Embargo-esque. Well, I like Embargo, and I think it might be an underutilized mechanic. I like Bridge and Highway too!
--The wording, names, prices, and secondary effects are completely up for debate. I just tried to make them a little different from Embargo for the sake of variety. I have not playtested these at all.
--Inflation only affects Kingdom Cards, while Surplus can be on any pile. This is to avoid situations where Coppers cost $12 and the game stalemates. Although that would be pretty hilarious.
--Should this only affect cards until the pile runs out?
In any case, I think it's an interesting idea that could be an interesting option in certain situations. You could play to make your opponent's strategy more difficult or your own more viable. Certainly there would be exciting interactions with remodeling cards, Workshop, Band of Misfits, Border Village, Knights, etc. It's like a permanent, asymmetrical Bridge (or anti-Bridge)!
Let me know what you think!