Seems like a good buy if you think you will actually use all those filters. They are $170 on their website.
The kit goes all the way up to a 9-stop VND filter (ND512) so there's probably a few combinations in there you will never use unless you get into some long exposure photography in extremely bright scenarios (hard to think of a video scenario that would need an 7, 8, or 9 stop light reduction). The polarized filters you probably won't use as much due to the difficulty of using them on drones in general, but they are nice to have just in case, or if you do lots of stills photography and have the time to carefully set up your shots beforehand.
DJI charges $100 for a set of 4 (non-variable ND) and the cheaper third party brands are around $50-70. If you paid $120 that is a good deal as long as you think you will use most of them. At the end of the day it probably isn't enough money to matter too much either way, and since you got a bit of a deal so it's not the end of the world if there is one or two you don't use.