Quote Originally Posted by UKRob View Post
The bulb refers to shape of the knot - think light bulb compared to, say, today's Shave of the day photo by Celtic Crusader where the brush is more fan shaped.

As to why they charge more - you'd need to ask Thater.
The bulb brush must be more "effective" because of the higher price. Although the regular non-bulb one looks nicer, in my opinion.