RCBS' response sounds like BS to me. I haven't seen one but I'm guessing that the RCBS transformer that you plug into the wall is most likely an AC to DC converter. That should filter out any line noise and you are not putting the 'house' AC into the scale.

Simple way to check it out if you already have a UPS for your PC. Plug your scale into the UPS outlet. Isolation transformers in the UPS clean up the power and filter the noise and spikes out. There are some out there that actually take the sign wave in, filter it, convert it to a DC output, and then convert it back to a close facsimile of a sine wave to run their sensitive electronics.

Sounds like RCBS just needs to spend $1.25 on their transformer rather than the $1.10 that they're currently spending.

You could possibly find a 'cleaner' transformer to power the scale.