I think it's certainly possible to have a VP card that counts the coin tokens. How many times did we say there could never be a VP card that counts treasure, then suddenly, Fedoum!
Man, I don't remember people saying that. I'm pretty sure I didn't. I thought it would be tricky, but doable.
I really do think the cost increasing mechanism would work here. Consider:
Cheese Destroyers' Guild
Victory -- $3
Worth 1 VP for every 2 coin tokens you possess.
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When you buy this card, you may pay any amount for it. For every $3 you pay greater than $3, gain a coin token.
The numbers could be tweaked, but it's a simple enough concept. If you pay $6 for it, it's worth less than 1 VP... OTOH, if you piledrive them all at $9, they're each worth 8, but only if you can piledrive them. Obviously another token gainer makes this easier to boost, but turning Baker into a cantrip 1 VP still requires three copies of this. Meanwhile, you opponent can ignore it, and use his/her tokens to smooth out their Province buys, while your deck turns green faster.
Aha! This is the exact card that I thought we were talking about all along (well, the numbers aren't important), and *precisely* the one I am sure you can't do. Yours, let's look at. You can't really use the coin tokens. I mean, okay, you can, but you are wasting $3 and a dead card in your deck to invest them for later at a 1/3 rate, and this is just a really really insanely bad deal.
Furthermore, there's no way you're buying one or two of these for the VP. $9 estate is very bad. Indeed, it's really hard to make $9, and if you spend $6 on them, you get 1 token. If you piledrive them for $6, they're worth 4 each. Now 4 for $6 isn't unreasonable, but needing to piledrive them makes this very unappetizing. Okay, let's say you can get 2 of them for $9. Now they're worth 5. Still a bad deal. If you get 4 of them for $9 and 4 of them for 6, they're provinces. Well, that's probably very roughly the same difficulty as piledriving provinces. I would guess it's a little harder actually, but well, it would be reasonable. But again, you have to piledrive them. And you have to plan on this from the start and commit to it. And most importantly, near the end, your opponent just drops $3 a couple times, just to deny you, and your strategy really crumbles. And again, you don't want to touch those tokens, because they are your points, they are far far to precious to use. So this card is just too weak, all around.
Of course, with another card that makes coin tokens, it might be broken still, or maybe just reasonably strong, but well, let's assume that that could work out - these games just aren't going to come up much.