A motorized brush for $70? Damn. I think you could have made one of those for 70¢.
This problem exists all through the industry, and the damm thing doesn't even work! Not just for add ons like this, but for everything. In Leeds for example there is almost 400% difference between 2 pro level photos printing places, the cheaper guy is not doing it for the love, so what is the more expensive guy trying to do? The quality is bang on at both places.
I think you have the right idea Mark, keep it simple, no gimmicks etc...
Cheers
Cris.