The strength of the card really depends on how your deck is set up, which then depends on the kingdom. If you have Chapel, Festival, and Hunting Grounds, then you can very easily build a strong engine and this card will make it even better (likely buying 1 or 2 of them). If you have Chapel, and not many engine components available, and run mostly Big Money, getting your "coin density" of your deck up to 2 or higher, then this card becomes super strong too, and you could probably afford getting a few of them.
But if you have no trashing in the kingdom, and maybe even cursing, then your coin density may never even get much above 1 (or in some cases, not even that high). At that point, the +3 Cards, take 1 Debt ends up averaging out to just being +2 cards, and then it's very similar to a Lab (on average... some turns it would be better, other turns worse). But unlike a Lab, you couldn't get very many of these, because when they collide they become that much worse (although in this hypothetical setup, you could probably just discard those initial estates and all the curses you've received, so maybe not quite so bad).
Is it strong for $5? Probably. Is it broken? Likely not. Have you tried playing it with "round up" instead of "round down"?