Hi Graz,
I do really like the 3nm Astrodon NB filters but they definitely come at a premium price (assuming you can actually get them... I just enquired at a couple of US suppliers and since Astrodon changed hands supply has been erratic.)
I think they are worth the price, especially for imaging from inner suburban Brisbane. Whether they are worth it to you is a question that's harder to answer
Cheers,
Rick.