I'm a mechanical engineering PhD who works on numerical computing, data analysis and the like. I've spent several hundreds of dollars on fonts. Because I like things being just so, because I like seeing the artefacts I produce being nice to look at, and because they're just plain beautiful.

Day to day, I use open source fonts that Butterick recommends. But once in a while, I like using just nice stuff. It's like a nice fountain pen for others.