Anodized would be nice but it adds a couple of complications. Anodizing adds a coating of up to .002 on the surface. That means you would have to produce two different models as the dovetail dimensions on the anodized version would be thicker otherwise. While anodizing isn't overly expensive, many anodizing shops have a minimum charge and to do just a dozen or even couple dozen bases could increase the cost significantly. Would you be willing to pay double the cost to have a black base over an non-anodized one? Probably not.

Because these bases won't be subjected to adverse conditions, end users could probably paint them black (with proper paint and prep) and have them look good enough.

__________________
So many S&W's, so few funds!!