it really depends on the routes and specific fares, even ignoring the availability of early morning/late night flights or existing accommodation in place (when I visit friends and relatives I don't pay for lodging).

For example, suppose you want to visit Budapest from Rome over the weekend[0].

If you fly out this Saturday, the flight is €10, you arrive at 10AM. If you want to whole day, you can fly out on Friday, for €23, and find accommodation for €45, totalling 68 euros[1]. Traveling by train is sadly way more expensive.

Consider instead Berlin -> Budapest, it's €10 on Friday, direct, with Wizzair, but >100€ on Saturday with stops. The train is both cheaper and faster!

[0] this is where I live and where my family lives, the route I fly most often

[1] prices are from skyscanner, airbnb