I think that the reason that Sandersons bring less than the Ropers is primarily because when collectors first started collecting custom grips they became aware of Roper first. The checking design of some of the Ropers is a little more "visually" attractive than the Sandersons but the workmanship is pretty comparable in most cases. And, as a general rule, the wood in the Sandersons is prettier than in the Ropers.

It's somewhat analogous to the Registered Magnum and the non-Registered Magnum. Why do comparable RM's bring more than non-RM's? There are certainly less of the latter than the former. Simply because the RM's came on the scene earlier and were first discovered by collectors before they differentiated the non-RM's.

Here is a pair on a first model K22.

Bob