That's kind of funny. French people is the single biggest source of expats (if we ignore domestic helpers) in Hong Kong. Seems to be very common for French people to emigrate.
Obviously I'm in a bit of a bubble (having done this myself) but a lot of my college friends left the country too.
I think you're talking about business schools. Almost all reputable engineering schools are virtually free, as well as all universities.
"Virtually free" can mean somewhere around 2000 Euros a year. A lot of people get aid (I didn't have to pay for my last year thanks to this). Plus most engineering schools don't really use textbooks, so you don't have much in extra expenses apart from a laptop.
Yes, taxes pay for this, but that was my out-of-pocket for schooling.
You do have to pay for some business schools, but what people say on that: you pay for your diploma.
I have friends who went to some private schools for computer science and it seems like it's a good path for some of them (around 8k euro/year)