Whether it aligns with the marketing or is part of the "Japan fascination", I think, is really hard to say especially as an outsider myself
There's a tranquility to the surroundings, but it's often disrupted by throngs of tourists.
we weren't prepared for the intensity of the sun, even on an overcast day. got chafed and sunburned after a day out, a reminder that nature has its way. that being said, immersing in the onsen was surreal in its relaxation, a balm for the burns.
In any case it was an experience, certainly not a cheap one, and it was punctuated with moments of discomfort but also deep relaxation.
Do you mean the onsen, or travel to Japan in general? Onsen are typically less than 1000 yen to enter - quite cheap for the relaxation they give you.
Fancy onsen ryokan can be quite pricy, but I wouldn't say it's expensive in general. I'm currently in Matsuyama and entry to the Dogo onsen bathouse (one of the oldest hot springs in Japan) is like 460 yen per person.
Many hotels also have hot spring baths in onsen towns without it being too expensive. Dormy Inn is a good example. That's a chain of business hotels which always comes with a bath in the top floor. Price is a bit more expensive than regular business hotels, but nothing over the top.
Personally, I'm a big fan, and I'd recommend everyone to give it a try if they can (but to also research the manners, rules, and exceptions - tattoos are a big no no in most public onsen). For those visiting an onsen for the first time, you can use a site like https://selected-ryokan.com/ (which includes private onsen) or (my recommendation) Booking.com to find something tourist friendly and read the reviews.
It is however, significantly cheaper. I think we can enter for like 500 or 700 yen.
The best I've been to have outdoor areas with snow falling, it can be so peaceful and relaxing.
What blows my mind is that some are crazy hot. I recall one where I could barley keep my feet in only to have some local Japanese kids jump in as if it was a play bath.
I found the ritualistic traditions around it to be calming. I spent a few hours at the one I was in and it was silent and almost meditative. I remember leaving afterwards thinking that I had a pretty much blank mind while there and was entirely present in the moment.
Best experience was going to one in the mountains, in the middle of winter, only person there, and sitting in the 40C water in a snowstorm.
1 was in a city and big and quiet plastic. 1 small suburban on that was very traditional and one near Fuji was about 50% outdoors. All were really nice.
I really wish we had something like this here in London.
Onsen are available at all price levels, and popular with blue-collar workers; they are not a high-class exclusive activity. It's not like having dinner with a geisha or something.