You can't just take one statistic amongst many and make overarching statements like this. Average brute salary is lower in Portugal (but not half, and then the tax systems are different). Portugal is a smaller market and the cost of living is also lower. Unemployment is much higher in Spain.

The reality on the ground is that both societies are quite similar. I don't know much about Greece -- except that it's the cradle of western civilisation. When did we start being so nasty to each other?