As a 30 year old iOS developer working in Rotterdam I earn about 43000 annually with a 40 hour work week. I do believe a should be able to get a bit more, as iOS developers seem quite rare in the Netherlands and I believe lots of companies are looking for good iOS developers. I should explain I'm not working in a startup - I would guess in a startup people would generally be paid worse.
If you understand Dutch, perhaps a good forum to get a better idea what would be an appropriate salary, you should check out the "Werk & Inkomen" sub forum of the Dutch technology website Tweakers.net.
See: http://gathering.tweakers.net/forum/list_messages/1446515/la...