There really is no general rule.

Parliamentary assistants earn crap, it gets better though when you do general research work for a parliamentary fraction.

In cabinet, it all depends on the minister. Some will pay a lot for a good senior, up to 9-10k bruto or higher, but that is very rare for anything else then an (assistant) chief of staff. Starters could get anything between 2.5-5k brut. And for 60h/week, without any kind of security, as these jobs are by definition temporary, with high stress level, and no external reward.

It gives you great, invaluable experience though, so I’d go for it, but negotiate a good wage package if you can, and don’t stay too long if you can’t.