Because we don't have the same costs as in the US (university, healthcare, housing, ...). For instance, the cost to attend courses in a good university in Belgium is at most 835 euro/year [0]. (This does not include textbooks)

In the EU, the market is much more fragmented because of the many languages we speak.

[0] https://uclouvain.be/en/study/inscriptions/tuition-fees.html