My DD wants to study Political Science in The Netherlands, either at The University of Amsterdam or Leiden University. She is looking for a career in The UN or Foreign Office.
Are these degrees any good or are the Dutch degrees taught in English just cash cows?
Look at the specific university, same as you would in the UK. Degrees taught in English from some Dutch universities are very highly thought of and as far as I know Leiden and Amsterdam are both reputable. While the fees are much lower than the UK (3K compared to 9K a few years ago) living expenses are higher and you have to factor in travel. Perhaps less obviously, the university system is very different. Even very good students can't assume they will graduate in three years as the coruses can be very demanding and they may have to retake courses - though they may be able to build up extra credits from summer school courses so as to graduate, which doesn't happen in the UK.
EU universities must charge other EU students the same fees as their home students, so surely not much of a "cash cow" there. Though if they attract non-EU English speakers they can charge more. UK universities do the same. Presumably after Brexit universities in both UK and Europe will start charging each other the (much higher) non-EU fees though I think the UK govt has at least promised not to let universities whack up the fees for their existing EU students.