The additional mandatory fees are around 30% https://sv.m.wikipedia.org/wiki/Arbetsgivaravgifter_i_Sverige https://sv.m.wikipedia.org/wiki/Arbetsgivaravgifter_i

The additional mandatory fees are around 30% https://sv.m.wikipedia.org/wiki/Arbetsgivaravgifter_i_Sverige https://sv.m.wikipedia.org/wiki/Arbetsgivaravgifter_i_Sverig... So with 4 kEUR gross salary you end up at 5.2 kEUR cash costs. Then there are also non-cash costs, like 5 weeks of paid holidays (or did unions actually achieve the 6th one? It's 30 years I lived in Sweden...) And you might need an office, equipment, and what not. So the cost can easily be 6-7 kEUR even if the developer sees only 4 kEUR on their payslip. A few might earn (significantly) more. But that's more likely in corporations higher levels than for open source related development work.