My Input:   I have two buffers..... One 3/4hp Baldor, and One 1hp Jet with extended shafts.   I WILL NEVER OWN OR USE A BUFFER THAT RUNS FASTER THEN 1800 RPM!    The cheaper ones are generally those that are too fast... they tend to be 3600rpm or faster.   The worst situation I can imagine a person placing themselves in...... a high speed buffer (more then 1800rpm) with a loose buff.    
 My "bad experience" came early in my career.  My first buffer was a 3/4hp/3450rpm.   Not long after buying it.....it grabbed/threw a blade THROUGH the shop wall, creating a hole big enough to put my fist through, and ended up about 20 yards out into the backyard.   AFTER changing my shorts, I unplugged it, took it off the bench, and gave it away the next day.    
  I do not buff anything other then guard and/or handle materials.  
BOTTOM LINE:  A buffer is the most dangerous piece of equipment you can have in your shop.  I have had TWO friends fatally injured by them, and every time I step up to use a buffer, I think about those incidents, and am far more cautious then any other function in the shop.    My advice is to ignore cost, and unless a buffer is 1800rpm or less, just DON'T.