And of the two US distributors listed for their products, one doesn't list the 6-channel attenuator and the other shows a list price of $487.

Riiiiiight. For $487 (more like under $200) I'll figure out my own ganged passive attenuator. SMD resistors don't impress me.

Much more likely is six channels of high-quality op-amps, or even a used 7.1 receiver with pre-in/outs for the 7.1 channels. $500 for a ganged, manual, passive volume control isn't even in the same ballpark as what I'm talking about.