APC props do need to be balanced! 9 out of 10 are bad enough to require a fair amount of sanding! The only prop I did not have to balance was my Mezlik 18X8, but then at $35 it should already be balanced. For the time it takes to balance a prop, the end result is worth it. I have seen the result of a 20,000 rpm centrifuge being thrown out of balance (1/4 oz weight) for testing. It went threw a wall! Yes glow engines normally turn around 11,000 to 15,000 rpm., but imagine the vibration on the airframe at WOT. Those screws that won't stay tight or the needle valve that won't stay adjusted can all be caused by an unbalanced prop (yes, been there and done that!). The vibration you think you can't see is what will shorten the life of the plane, engine and radio gear. Vibration will also cause fuel foaming and can cause RX crystals to fail (that's why they tell you to wrap the RX in foam). What other people do with their stuff is their choice, I like to make it as right as it can be because I can't afford to keep replacing things when it could have been prevented.