Welfare in the Netherlands is ~1200/month. If you live cheaply (e.g. in a 500/month room in a shared house) that leaves more than enough for a transatlantic plane ticket every now and then.
I cannot find the number you report on that website. Please elaborate on where you got it from. I'm 100% sure you are leaving out important additional details, like that one has to have been recently employed.
You can get WW (werkeloosheidswet - unemployment law) for 24 months, like you say you need a sufficient history of employment. This is based on 70% of the minimum (full-time) wage, i.e. 70% of 1615.80 = 1131 euros/month.
Minimum wage is on the top of the linked pdf (download link here [1]).
Sorry if I was unclear, just looking for some ballpark numbers for the sake of the argument.
This sounds too good to be true. Do you have any numbers? The welfare systems in EU are shrinking.