Do we have anything that is clearly useful and incredibly beneficial, but it requires a morally repugnant "cost" to use, (i.e. killing/torturing people), yet it's made clear that the Foundation uses it anyway, simply because it is so useful?
No, because that goes against what the Foundation would do, and magic items with drawbacks tend to not be very interesting.
On the whole, no, for the reasons stated by azzleflux above, in addition to the fact that the Foundation is very cautious and will never, ever, ever integrate an anomalous object into everyday usage. Even if it didn't have a moral cost, anomalous objects just are not used by the Foundation because they don't know that it's safe, they don't know that it won't one day randomly bite them in the ass.
Even though people's headcanon for the Foundation varies, one thing that I've seen as a constant is that the Foundation isn't cruel. If the Foundation ever needs to do something completely and utterly morally repulsive, it's always because it needs to be done, because if it wasn't done more lives would be lost. A 'few for the many' ideology, if you will. They would never sacrifice innocent human lives for the sake of their own convenience.
Foundation is very cautious and will never, ever, ever integrate an anomalous object into everyday usage
Giving bearhugs to the unsuspecting since 1872.
Fair point. I guess "never ever ever" was a bit much.
But still, if the object hasn't been explained, I can't imagine the Foundation would take the risk to use it for themselves.