I hate having to tear into these and find decent brushes on some and other needing to be replaced.
I understand your comment, but I suggest a different mindset.
At my wash, vacs are a very important contributor to revenues. As such I do routine/preventive maintenance on them, including replacing all the brushes every 12-18 months. It takes a total of an hour and costs me $49.50. ($1.77 per brush * 28 brushes when I ordered them 2 weeks ago.)
In most cases the brushes are 1/2 to 3/4 worn out, and I replace ALL of them anyway. Most of my motors last 5 years or more, some have gone 10 years. The motors I use are $45-50.
IMO it is worth spending $50 to virtually eliminate customer "this vac has no suction" phone calls + a service trip to the wash, not to mention saving $ on motor replacement. Bottom line: except for that 1 hour once a year or so, vac motors are a non-issue for me.