As the other answers say, astronauts are public employees and earn their salary as public employees. They do not receive specific money for traveling into space.
Returning to Earth (literally), Armstrong retired from NASA and worked as a university professor of engineering and a consultant to private companies.
Buzz Aldrin fell into depression and alcoholism (among other things) and ended up selling Cadillacs in Beverly Hills to support his income. As I once read, he did not sell any. His grandfather and his mother also had mental problems and committed suicide. Fortunately he recovered from his problems. However he is by no means rich. As far as I know, his income comes from the publication and sale of books, from presentations at conferences, and from the sale of autographed memorabilia. It is relatively easy to acquire a Buzz Aldrin autograph.
He recently put up for sale more than 60 items he kept from the Apollo 11 mission, including the jacket he wore inside the lunar module.
The sale of personal belongings of astronauts today is much more common than it seems. Many astronauts with or without agency permission take items to the International Space Station to sell as souvenirs when they return, either at auction or even on eBay.
I was left with a square eye and was a little disappointed to see the International Space Station being used as a souvenir sales attraction.
I don’t blame the astronauts, I blame the agencies because maybe they don’t get paid enough to risk their lives. Imagine how their salaries must be to supplement their income from the sale of souvenirs.