You want to read this thread.
I think the thread is about more powerfull cards than dicussed here. Cache perfectly proves that you can use the "cursing" of your deck to balance the price of a card.
I agree in general, that the other thread of balancing otherwise disgusting cards (pre activated cities being a good example) with a negative VP gain doesn't work. In particular, I think that any card that makes total deck draw engines more viable is probably not going to be balanced by tacking on some negative VP, because of the ease in which they could then be removed. However, this card isn't obscene in power, and doesn't really facilitate that type of game.
Comparing this card to Cache is valid, and I agree that this card wouldn't be a game breaker from a power creep perspective.
That said, Cache is already considered to be a bad $5 (near the bottom of Qvists rankings), and I would assume that this card is actually worse than Cache. (How many times have you discarded to torturer when you could have bought a gold if you had gained a curse?). Cache is viable when the extra coppers are a bonus vs. a hindrance. I'm struggling to find a reasonably common situation in which I would willing buy either of these cards, but skip Cache in favor Blood Money (in the $5 gold that gains a curse variation). The traders / watchtower scenarios are neutral / favor cache. The best I can do is picking up 2 varieties of cards to push your fairgrounds over a threshold, and that just doesn't seem interesting enough.
It's not "strictly" worse than cache, because 1 card gunking up your deck is better than 2, but I'd say it's probably similar to Hunting Party vs. Lab in terms of % of time that one card is better than the other. Unfortunately, lab as a medium grade $5 has room for power above it... and cache as a bottom tier $5 has little room for stuff underneath it.
A straight "-2vp" on the card would be interesting. Yes - I know that Rinkworks feels that its unbalanced with presence of trashers... but remember that you still have to get that trasher and this card lined up. This card would be far from an auto buy, even in the presence of trashing (with or without benefit).
Other penalties that could be explored in favor of making it more interesting could be:
On gain - all players draw a card (and discard one if that turns out to be to good?)