How about 5VP if you have at least two potions? The only situation where buying more for VP would ever be worth it is Vineyards, which don't need a buff.
You're right that you probably wouldn't want to buy more than two Potions for VP in most situations, but I'd rather keep it as-is just to allow for some variability. It could be useful in some endgame scenarios as an alternative to Provinces or Duchies.
Are you concerned that this would encourage players to empty out the Potions pile? With Bibliotheca, Potions are potentially worth slightly more than Obelisks. I think that's fine because more often than not, having multiple copies of an Action card will be more useful / less detrimental than multiple Potions.
Unfortunately, the majority of games don't have Potion cost cards, and thus no Potions. It would need a special set up.
For the purposes of this contest, I didn't think it would be an issue since if this is added to Alchemy, then chances are you would have a card with a Potion cost. In any case, I take your point and will add a setup clause to add Potions to the Supply if not already on the board.
that seems like to much vp for potions to me. 2 potions is 8 money, , and 8 money for 5 vp is a good deal. i fear that potions will keep being picked up too much untill endgame and risk dragging the game out.
also, there are plenty of games where 1 potion is the optimal number, so having it be per 2 potions might give novice players the wrong idea and maybe burn them on potions. i think i like just giving "2vp" per potion more . i am by no means an expert designer tho
8 money for 5VP is a good deal, but worse than buying a Province and moreover you clog your deck with an additional card (granted that you can spend the money on two separate turns).
It also seems like you would get better slightly value with Potions ($0.625 per VP) than Duchies ($0.6 per VP), but this is mitigated by the fact that you need more buys to get sufficient Potions and you need to ensure that you have an even number to optimize the scoring.