Stamp collecting has been around since the mid-19th century.
It's still a huge deal when a comic book breaks $1m at auction. But there are lots of examples of stamp collectors paying that kind of money.
Coin collecting, too, is a far larger hobby (by $ value) than comic books.
Which are the most valuable stamps and coins?
ERRORS AND UNINTENTIONAL VARIANTS ARE WHERE THE HUGE MONEY IS IN THOSE HOBBIES.
Here are two examples.
The first is the "Post Office Mauritius" issues, the first stamps from Mauritius. The intention was that they read "Post Paid", but they were mistakenly inscribed "Post Office" by the local engraver.
Very few were sold before the error was put right.