I’d imagine you shoot for less than a second at a time. It’s pretty hard to line someone up for a long time since they’re trying to dodge. Even a 1s arc would cover a lot of ground if you’re pulling the stick. Strafing runs in movies often are less than 10s too.

Where do you think this technology originated? Snapchat?

Sounds like you can build one for $400-1000 and a week or two of work. Doesn’t seem overpriced to me… I guess it depends on the precision and quality of the build. I’m sure you could make one with Lego mindstorms if you want to.