While I can't help with the washing question, I can throw out some information on my experience with the CA Duster.
I have three of them, two of the wood handle original style, and one of the wood handle "Super Duster".
All of them are around 10+ years old and one of the originals is close to 20 years old and all seem to work fine.
I don't wash them, but I do beat them on the side of the trash can several times during use and when I'm finished. I also don't try to remove dirt/dust that really needs to be washed off. If the vehicles are dusted daily, it doesn't seem like you pick up all that much dust in the CA Duster itself.
There is a difference between the original wood handle duster and the so called "orignal" with the plastic handle. The yarn on all three of mine is almost twice the diameter and about 50% longer than the yarn on the $10 dusters. Is the difference enough to justify twice the price? That's for each to decide for themselves. I might use one of the cheaper ones for the interior, but I still would buy the more expensive one for the exterior. I have never owned one of the $9 ones so I'm not knocking them. It's just that I have been so satisfied with the ones I have, that I'm not likely to change. FWIW, I did buy one of the small "Dash Duster's" and didn't think it picked up the dust very good. I rarely use it.
One thing about washing one, what do you have to lose? You can still throw it away if you aren't happy with the way it works after washing. Just try it on a small area, (maybe the car of someone you don't particularly care for), before you do your entire vehicle.
Charles