Very cute, we as Ameicans are use to places with a lot of space. There are places people live and they live in very small close quarters. I think the average guest house is maybe 500 sq ft. In California, you can build a guest house, but it may not have cooking facility, those are what they call Granny Flats if you can cook in them. It crosses the city planning line, of a lot being for single family dwellings. Having a second place you can cook in, makes it 2 on a lot, which our city classifies differently.
My friend and I, when we went racing in Pikes Peak, Colorado Springs had hotels that were small individual house bungelows. They were real cute, maybe 350=400 sq. ft from the 1950's. Simple shower/sink/ toilet. the cooking facilty was a combination small sink unit with a electric stove, all one manufactured unit. I do not think any Californian Code would allow mixing of electric stoves and water, but it was way to cook, had a small refrigrator, and tiny table with 2 chairs. The were very small, cute for a single person or couple. The one in your picture if it cost $95K for 365 sq. ft. that is pretty expensive per sq. ft. actually. When I built my addition, I discovered the majority of your money goes into the kitchen and bathrooms. Thats where all the big ticket items get bought. Everything else is framing, windows and drywall. The other place your some goes is in the level of quality of your windows. We spent a lot of money of Marvin wood Windows, but you can buy energy efficient metal framed windows for a lot less. You can probably build bare bones standard constuction little houses, less than 1/3 the price of the one you showed. It would not have be fancy, but it would be functional.
In todays real estate, maybe there would be a big market for tiny homes, with very little lots, no parking garage. Could be a alternative to apartments. I guess the idea of Condos was as close as we come, but look at there prices. We are talking things a little bigger than a shed building.