Per usual, I have no idea who made it, but it wasn't me.
I remember the thread. It's worth looking for, because it has a lot of neat cards - sadly i couldn't find it immediately. I must admit, i'm not a fan of the concept. It seems gimmicky and buggy, and for most cases, you could just replace the Reaction with the simpler "When you would gain a card, you may discard this to gain a card costing $1 more, instead.".
This would include any +$X and any "gain a card costing up to $X". It would not affect things like Knights (Hooray, let's trash Provinces!), Pirate Ship (Hooray, wording implies doubling!) or cost reducers (well, still kind of) but that's for the better IMO. Many of the interactions are also plain weird. What happens if i use this on Apprentice's non-number coin icon? If i Process Catacombs, can i use this to raise Catacomb's price to $6? It the price such a symbol, even? It certainly looks similar. And how long does it stay that way? If i play Highways and let it say that cards may not cost "less than $1", does Copper actually increase in price?
Patron isn't the worst idea in this design space, but i think the design space itself is not a good one. Donald dropped the idea for a reason. And again, i think most of the time, it's just going to be the reaction i described above.