I don’t see the point of boom arm unless you are working on site. In the shop it is much simpler and secure to suspend the hose and cable from the ceiling. A piece of rope and hook will give you a comparable swing. Stretch a cable across with a sliding carabiner if you need to move across large shop. $300? Really? 
I am looking at boom arms, brand name and especially shop made and wondering. They all consist of large diameter pipes. Why attach a hose to it if you could channel the air right through. Connect the vacuum to the bottom end and a piece of hose to the upper end. That will save you 2.5 m of hose. Also, pressure loss through wide smooth and straight tube will be lesser in comparison.
How do you handle hoses and cables?

I am looking at boom arms, brand name and especially shop made and wondering. They all consist of large diameter pipes. Why attach a hose to it if you could channel the air right through. Connect the vacuum to the bottom end and a piece of hose to the upper end. That will save you 2.5 m of hose. Also, pressure loss through wide smooth and straight tube will be lesser in comparison.
How do you handle hoses and cables?