What are your unpopular and expensive hobbies?

I have a hobby of collecting mobile phone cases. Every time a mobile phone manufacturer holds a new product launch conference, we will delve into the mobile phone case. Because there is no money to buy a mobile phone, haha, I can only collect unused mobile phone cases bought by my friends. When my father was a child, the price of a Nokia N3 was several thousand, especially at that time, the consumption level was not particularly high, so I was particularly excited to collect mobile phone cases when I was a child.