Also data roaming:
- 10 MB - 24 hours valid € 2
- 200 MB - 7 days valid € 15
- without bundle € 0,54 per Mb. (billing per Kb.)
So it is easier to extend the validity of the SIM by just using the browser for a moment.
More info:
http://www.bliep.nl/static/pdf/tariff.pdf (in Dutch, sorry!)