Pretty close one:
Alchemist:Laboratory::Treasury:Peddler
Yeah, though I think Walled Village:Village is closer—WV is a Village you can topdeck if you didn't "use" the extra action; Treasury is a Peddler you can topdeck if in some sense you didn't "use" the extra money for increasing your score. The equivalent for a Laboratory would be something like "If this is in play at the beginning of your cleanup phase, you may discard a card from your hand; if you do, when you discard this card from play put it on top of your deck." (Actually, that sounds kind of cool but way more powerful than Alchemist.)
Conspirator(activated):Peddler::Grand Market:Market
Border Village:Haggler::Village:Silver
Hmm, so what I was thinking of for Conspirator:Peddler was Conspirator is easier to
play after you play several actions, whereas Peddler is easier to
buy after you play several actions—I wasn't actually thinking of their effect when played, though of course your analogy works for that. ...What do you think of Conspirator:Peddler :: Throne Room:Talisman? (Easier to play:easier to buy :: play something twice:buy something twice?)
I'm not convinced by Border Village:Haggler :: Village:Silver; Border Village is "gain something cheaper
when you buy this, and Haggler is "gain something cheaper
when this is in play".... maybe Farmland:Remodel?
Not perfect, but I really think it fits:
Venture:Adventurer::Bank:Coppersmith
Perhaps a bit of a stretch, but just ignore Upgrade's +Action and it sort of works:
Upgrade:Remake::Jack of All Trades:Trading Post
I kind of like the Jack of All Trades one. I don't really get the Adventurer one?
Scheme:Throne Room::Caravan:Laboratory
I like it! Or maybe even better, Wharf:Council Room?
Two more from me:
Gardens:Philosopher's Stone :: Estate:Silver
Courtyard:Ghost Ship :: Horse Traders:Militia, except the numbers of cards don't match up right
And another conundrum: Ill-Gotten Gains:Embargo :: ??