From what I can see online, the average compensation that an au-pair in The Netherlands receives is 300 euro per month, with living expenses being covered by the family. There is no minimum wage requirement for au-pairs like in the UK or the US.
Working abroad is a totally reasonable proposition compared to working in the Philippines.
A normal full time employee costs at least 2000€ a month (salary, tax, pension plan, health insurance, etc). If you are paying less than that you are definietly exploiting them.