I was given one as a gift about a year ago, and I can confirm they work. Looking up the price of mine (back then), it was something like 70 dollars. I'm surprised they have it shown at 30k yen; seems astronomical.
Either way, it surprises me is how little they actually talked about it here though. Sure the tension release is real, but it also promotes blood flow movement to the spot. And really, this helped me with recovery when things went wrong from a pulled shoulder muscle and jumper's knee (inflamed patellar tendon). At the very least, it seemed to shorten the recovery period compared to other times i pulled a muscle by a couple days (7-8 days instead of about 9-10). And I'm older now compared to the last time I tried (and eventually failed) to keep a steady workout routine.
This is on top of general muscle soreness reduction from 2-3 days to 1 less. This is inclusive of muscles that I never specifically targeted before and focused on for the first time. Or days where it's not a workout, but just doing physical work/labor all day.
All that for like a minute or two max each day, 15-20 seconds per spot.
I'm really not trying to sell the thing, nor am I particularly healthy or that fit. But ultimately, saying more how it works, and what it did for me specifically in the last year. "Tension release" and stiffness reduction isn't quite enough. Though I imagine they purposely don't want it to sound like an advertisement, because reading what I just wrote, self explanatory.