OK strange noise

On my 2003 Prius I had a brake warning light and constant warning tone. I didn't have much history on the car, and wasn't very familiar with their general operation. On a hunch I placed a screwdriver handle on the booster pump assembly (on the passenger side of the firewall) and tapped the screwdriver handle with a hammer. To my delight, the booster pump kicked on and ran enough to build pressure and the brake warning light extinguished (along with the annoying warning tone). Unfortunately it was short lived, as the pump only operated that one last time. Since I knew the pump assembly was bad I went ahead and removed it and inspected it. I disassembled the section with the electric motor and found that the commutator bars were extremely worn (some copper commutator bars were totally missing). I searched around for parts online because I found a used booster assembly to be expensive and possibly no better than my booster. What I found is that you can buy a new armature assembly to replace the worn one. The mid 2000s 4runner and GX470 used a similar pump assembly for the ABS system, so I used an armature for that application. I've since put 23k miles on my car and have had no further issues with the braking system. So I'm basically saying if you can determine that the motor isn't running, you should probably look into replacing the motor/armature section of the brake booster pump. I'd imagine this is probably the source of most brake issues due to the age of these cars.