On the same € 65.000 gross, a worker takes home roughly 21 490 zł more per year in Poland than in Netherlands. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Poland has moderate rent pressure, while Netherlands has very high rent pressure. That keeps Poland's nominal advantage closer to a real-world advantage.
Healthcare and pensions go in the opposite direction. Poland runs a public healthcare model — NFZ public system with growing private supplements. Netherlands uses a public model — Mandatory private health insurance (~€140/month) with regulated coverage. The country with lower take-home often shifts costs that the other country leaves to your private budget.
Net-of-everything, a relocation decision should weigh strong public welfare in Poland against comprehensive welfare state in Netherlands, plus differences in pension capture, social safety nets, and city-level cost of living.