On the surface, Sadistic Sacrament is an efficient way to deprive your opponent of 3 cards for only 3 mana. But the kicker which costs 7 extra mana lets you absolutely ruin your opponent’s deck, by allowing you to exile up to 15 cards of your choice from their library. While that’s a lot of mana, having that option in the late game is pretty sweet.
Most recently, Sadistic Sacrament has seen play as a two-of in some decently competitive Vintage lists on Magic Online. While it’s hard to say if Sacrament will ever find itself in a Modern Mono-Black control list is hard to say. But a big winner in a major Magic Online Vintage tournament using it could cause a bunch of copies to be bought up in a hurry.
On the paper side of things, this is a card that’s been worth $1-$1.50 for a very long time. They simply aren’t printing more of these. It sees a fair amount of play in EDH, as well. While Vintage isn’t really a big deal in paper Magic anymore, if it even sees a hint of play in Modern at top tables, speculation could cause it to potentially spike in price. Otherwise, it's just a nice rare card to have in your Magic collection.