Depends on what you are trying to achieve. Just want plinking ammo or something that groups good to 100 yards and in, then no. Want extreame precision and to shoot longer range, then absolutely.
I reloaded for probably 10+ years before I bought one. Not only did it help me to see what my reloads were doing and to help troubleshoot issues, it really helped with load development and finding accuracy nodes. It is what lets me shoot those tiny little groups at those long ranges.
You can have tight groups at 100 yards with an extreame spread, but start shooting longer ranges without knowing that, and you may think you are just a bad shot when it is just a load your rifle doesn't like.
Using a chrono will speed up your reload development and will lower your cost of development as well.
there is a lot of things that are not necessary to load decent ammo. a lot!
but many of us want to get a little better than decent. it may matter on paper but not to bone and muscle.
this is something i try to get across to new reloaders. not everyone will get as deep down the rabbit hole as others and yet they will still build ammo good enough to satisfy them selves.
but a chrono can be handy and not long ago it would make a pretty good de liar out of ammo companies!
If you're trying to develop stable loads for longer ranges they pay for themselves pretty quickly. You can establish velocity nodes quickly with a low amount of shots instead of wasting ammo shooting distance to determine a velocity based on ballistics and impacts to find out you haven't achieved your goal. Saving barrel life, cost of components, time, etc. all adds up to a worthwhile investment, in my opinion.
Not necessary but incredibly useful. I use ladder tests, watching velocity change over a change in powder weight, to identify nodes to test for accuracy later. Only complaint I have with the magnetospeed is that it changes my POI when attached, so I verify accuracy without it. A Labradar solves that problem, but at a much higher cost.