How did mobile phone get so cheap?

My father brought a nokia phone that was priced 240 dollars on 2003 ( I think ). It didn't have good screen, have to use buttons, had very) ow storage. 15 years after I got a xiaomi redmi note 5 dual ai smart phone. It had great display, toch screen, it can do many things that my dad's Nokia couldn't it was made of aluminum. How did phones get so cheap!