It is a mixed bag: apartments can be pretty expensive, especially in Greater Tokyo area. Food is pretty cheap IMO. Taxis are prohibitively expensive, but railroad system is really really good and compensates for that pretty well.
But people don’t go to Japan because it’s cheap – it’s just a really nice place to live for some.
Apartments even in Tokyo are still quite cheap compared to today's rents in major American cities, and not needing to own a car also cuts living expenses massively compared to living in the US.
Someone coming from a German city with good public transit might not think it's that cheap though. But a lot of digital nomads are Americans.
Poking around sites online it was quite easy to find apartments fairly centrally in Tokyo for $1000-1300/month if you were staying for 3-6 months. While that is far from cheap, I certainly wouldn't call it expensive in the grand scheme of major international cities.
My relatives built a house in Tokyo which was absurdly cheap (£300K), but maybe I'm just used to London prices. As you get out of the major cities, akiyas can be basically "free", although will require a huge amount of time and effort to make habitable again.
Apartments are way cheaper compared to other major US cities. They're probably smaller though but the convenience makes up for it. You can also find something as low as $300 in Tokyo if you are fine with a very long commute to the station. I used to have a sharehouse apartment in Shibuya for $600. Shared kitchen, bathroom and shower. It was pretty good considering I didn't spend much time at home other than to sleep.
Maybe it’s selection bias, but pretty much anywhere I’ve been lately taxi (or actually ride hailing) is at least pretty affordable. E.g. a half hour ride I took late at night in HK was US$30, and about US$10 in Singapore. In Tokyo it was $60.
Depends on how much space you need to live. If you are fine with very little space, Japan is actually pretty affordable. Cheap food is good/health. Public transport is cheap and good/great. Lots of activities to kill time for cheap. Not sure about health care though.
Japanese salaries are very low (compared to the US). So if you’re coming from North America, local prices combined with exchange rates make it super affordable.
I visited Tokyo from London recently and found it to be much cheaper. A decent meal is half, or less than half of what you would pay here, not to mention healthier. Another comment mentioned taxis are expensive, but I found the opposite, my journey was cheaper than it would have been in London, and the drivers are much more professional. As for apartments, you can live much cheaper and more centrally (~£1500 is the minimum you need to play with if you want to live in central London.) Public transport is also cheaper, faster, and more reliable.
So yeah, on the whole, Tokyo is like half the cost of London and you get more for your money.
I had never felt so safe while I was there. I knew I didn't have to check over my shoulder, or walk down a side road if I wanted to use my phone so as to avoid having it grabbed from my hands. When I rented a bike, I could simply park it up without a lock, and knew I would come back to see it exactly where I left it. I forgot my bag in a taxi and got it back the next morning by going to the taxi office. I left my umbrella on a chair and came back to see it exactly where I left it.
It's how living in a civilised, first world country should be.
Yes, phone theft is rampant in London. The thieves are rarely caught and if they are, they get off lightly. Or released early from prison, because our prisons are full.
Answering your comment seriously, with an appropriate level of flippancy:
On the Tokyo metro this year I saw many advertisements for hair issues; lots of ads with balding noggins, contrasted with thick gorgeous heads of hair that you can acquire by making an appointment through a (naturally!) Japanese domain. In London, meanwhile, I saw zero ads for any hair-related products or services on the tube. Though if there were, I would imagine most would be advertised with a UK TLD.
But people don’t go to Japan because it’s cheap – it’s just a really nice place to live for some.