Don,
I think both are not to hard to find, the one with ridge being the more common one. It is just that I don't have one without ridge.
But this is also due to the fact, that, in the first place, for collecting BH's I am living in the wrong part of the world.
With my limited sources and resources I always prefered to take a completely different head before getting every single modification of one particular type.
Money-wise both are low grade heads - most often not reaching $10. But I think the Little Shaver's have great eye appeal and are of unique construction. This makes them a "must have", not matter if expensive or not.