Single Comment

I could think of several possible explanations why the value difference C-A
is much smaller than R-B.

1) B is the only piece of the four that is color bound.
2) B is the only piece of the four that has no mating potential

Unfortunately, repairing any of these two shortcomings of the Bishop, e.g.
by giving it an extra backward (bW) non-capture or capture did not seem to
up its value very much.

The hypothesis I currently favor is that there is a very good synergy
between Bishop and Knight moves. The Archbishop is extremely efficient in
gobbling up Pawn chains.