If one is somewhat flexible then flying really isn't expensive in Europe too. Just checked Google Flights, and starting from Vienna it would cost 29€ to either Rome or London, 50€ to Malta and ~60€ to some Greek places, return flight inclusive.

Safe 20€ a month, which is possible for a huge chunk of the population (easily > 80%), and you can do four to eight of those flights a year and that's just the lower end of the estimation, most still just don't flight that much here, and it's IMO really not an income question.

It's more like an ecological footprint and also time question as flying adds an ineligible overhead one can often outrun by using the good train networks, well maybe apart from Germany where privatization really killed a lot of networks and quality during the last decades, plus I can get to a nice nature area within an hour easily, so why bother travelling as long to the airport to only then endure their security theater.