I don't know if whether the numbers you quote for Romania are correct or not (Polish salaries for devs are not even remotely close to that), but a salary that nets you €4k/month after taxes is not very common in Sweden - which is considered a richer country than Romania.
The difference between Sweden and Romania is not between Swedish and Romanian software developers. It's between Swedish and Romanian janitors. The Swedish ones probably make 10x what the Romanian ones make. And most people in Romania are closer to the janitor salary wise, than to the software developer.
