Sorry but I have never heard about people's net pay. It's always gross. Everyone has their own combination of tax deductions and benefits, it makes zero sense to talk about net pay - everyone is gonna have something different. And from employer's side, I can't simply tell you what your wage will be in net - that's usually different month by month, depending on your family and housing situation, health/fitness benefits, education status etc. That's why business is so hard here - I had to maintain an army of accountants to do a small simple business...
only america has "04/15" - in every other normal place you talk about actual REAL money, not fictitious money you ain't ever going to see... there are no "deductions" to speak of or anything like that. benefits are federal, HI is taken care of etc etc... only america is all weird about all this (but it is ingenious as you discuss your salary as if you make twice what you do - makes every feel good about - "hey I make $300k" and you actually make $150-$180 depending on state/locality you are at...).
Americans have far higher net worths and disposable income after taxes and social transfers including healthcare according to the EU's own OECD statistics.
I know for a fact pre-tax pay is the main number employers discuss. Your sister is doing something wrong.
You would not make 3/5ths of 800k in the EU. If you are lucky - 30-50% of that, pre-tax.
You clearly haven't looked at living in the EU too seriously, evaluated the job market, run the numbers, etc. I have because I was evaluating this for my LDR. I make 1.2 here in the US (unusual circumstances; nominally 600); I'd make a maximum of 250-300 in the EU for a top offer for the same position.
I get taxed at 55% effective here in commie California but it wouldn't be much less in the EU, while my pay would crater. My fixed costs wouldn't be much different either. Food might be nicer though, and I'd be closer to my LDR. But the EU's long term economic prospects are terrible in the tech space. Insane regulatory overhead means that my company rarely even bothers with deploying new features there.
my sister lives in Europe and so does most of my family. they do not EVEN KNOW what their pre-tax pay is!!! when she interviews and does salary negotiations the number she gets is the number that will deposited into her bank account that will be at her disposal.
several years ago my sister needed a visa to go to UK and they actually asked for this - part of the paperwork was asking for her pre-tax earnings. it took her about a week to figure out where she could get this from...
