According to this website, the net pay on €11,000 is €6,510, so there's two possible explanations:
- the tax has been calculated incorrectly due to it being his first month in the role - I would imagine this will resolve itself with time, if the Irish authorities work like HMRC
- he's paying a very high pension contribution
Given that the average wage, per month, in Ireland is €3,750 before tax and €2,957 after tax, I'd be careful about complaining too loudly.
€11,000 is the equivalent of £9,723. Net salary in the UK on this, excluding any pension contributions, is £6,115 (€6,918). Compared to what the Irish tax calculator is showing, it's €408 (£360) per month more tax than the UK.
These are really things that should be considered before taking a job or making a move.
It's all good and well being told a gross salary, but the most important number is what is going in to your pocket.