John Bernhardt,
I have heard for years that riding mowers were labor and time savers, which equals savings.
I've also heard that the riding mowers can cause compaction, that the turn arounds can stress the greens and damage the edges more than the walking mowers.
I don't know if there is an incremental cost savings, and what it would be, net of all considerations, but, I've always felt as you have that walking mowers produce better conditions.
Seeing as how the greens are the most important feature on a golf course, any incremental cost to maintain them with hand mowing would seem to be money well spent.
But, I've been surprised by some of the clubs that use riding mowers.
Perhaps some superintendents can provide their imput relative to cost and effect.