4-6k seems high even for Helsinki. For starting position you can expect 2-3k, then as you build towards seniority you can get to 4-5k range, but you can expect to work for 5-10 years before you get to that 5k/mo (before taxes).
Now all kind of exceptions will come out the wood works telling me how they are "easily" making 10k/mo by doing something and working for someone who they won't admit. Yes even I know someone who is (or at least was) making 10k/mo, but he was very specialized expert, actual 10x developer. Most people are making far less. 3k/mo seems like the most common salary (again before taxes) for generic tech job.
Now all kind of exceptions will come out the wood works telling me how they are "easily" making 10k/mo by doing something and working for someone who they won't admit. Yes even I know someone who is (or at least was) making 10k/mo, but he was very specialized expert, actual 10x developer. Most people are making far less. 3k/mo seems like the most common salary (again before taxes) for generic tech job.