Because its a console which also is a mobile device. It not only comes with one controller, but, depending on the game, the JoyCons allow two players to share them. Without buying additional hardware. They also happen to be complete Wiimotes with motion tracking - something you had to buy extra before. And of course, it is the best and most powerful gaming hardware made by Nintendo. A PS4 is cheaper and has more GPU power, if you don't mind it being a big box. And it doesn't play the Nintendo games.

the joycons are real controllers too :).

So far I don't want to switch to a classical controller. Especially since I use the gyroscope of the right joycon in order to aim more precisely.

You don't need to buy an extra screen or controller, and it is mobile. The price seems fair to me.

Because it's not a loss leader. Both the ps4 and xb1 sold for a loss the first couple years of their existence.

Are the joycons not real controllers?

Current gen consoles you have to pay extra for a real screen.

Because they have legions of rabid fans who not only buy their products regardless of quality, but act as an army of apologists for them. The result ironically, is that unlike Sony's harsh lesson learned around the PS3, Nintendo has no such backlash to fear.

The worst they can do is just own the portable market, and sell a few iterations of a console to their diehards, which are numerous.