The first thing that came to mind was "All right... all right... but apart from better sanitation and medicine and education and irrigation and public health and roads and a freshwater system and baths and public order... what have the Romans done for us?"
But yeah, all the things you mention. I think it's conservative but not unreasonable to use as a rule of thumb that your net take home is about half of what a 'naive' calculation would net you. Especially in the beginning where you need to reserve a certain part of your revenues as a buffer for economic downturns; 6 months at the least, better a year. Back in May/April, it was the contractors that got the boot first. From what I can tell in IT they've mostly rebounded, but in previous crises that didn't happen so soon.
And you can either choose to work with a middle man, who will take a sizeable cut of your revenue, or do your own customer development, which takes a lot of time. Yes there are people who work for the same customer months on end for many years, but a) that's dodgy from a tax perspective, and b) in those cases you generally don't get to charge e1000/day.
All I'm saying is - grass is always greener on the other side. Yes as a contractor/consultant you'll make (a lot) more as a programmer in Europe, but not as much as the proverbial e1000/day rate makes it out to be.