Not only they are cheap (~1k karma per piece), they also have really good stats that you can "pick". What meant by picking is that you can buy any race's cultural weapon and they all have different secondary stats (for the most part). Say if you like precision, you buy the human one, if you like healing power, you buy the Norn one. If you like the Charr's huge blade, you buy the charr one. Unlike the cultural armor, the weapons are not restricted to race and barely cost anything and probably one of the best upgrades you can invest for your character.
Here is a guide with directions on how to access each cultural armor/weapons and some pictures of the cultural weapons at the bottom if you prefer to pick based on looks. Enjoy!