This bundle with GCU is by far the best deal on JoyCons I've seen since the system has been out. I think I've seen people say they have seen some of the gray ones on clearance at Target for around $50 (maybe less even) but with Target clearance it's always pretty YMMV. I think they have gotten around $60-$70 before too, but if you still have GCU this a great price for the game and pair of JoyCons.
If I still had GCU I'd buy this no question. Without GCU though it's still a good deal, I don't really need another set of JoyCons, but I do want Super Mario Party and this is better than spending $60 on just the game. I just don't see myself playing the game often and only bringing it out with groups, which I suppose is the purpose anyway.