There's another issue besides the high cost, and that is the sheer volume of solid waste generated. That factor kicks it out of the running for boondockers who are unable to burn waste, which often happens when there's a stretch of rainy or snowy weather. I can easily visualize a nightmare scenario with all of this human waste piling up inside the interior of the van and no place to put it. Ugh. I can carefully manage my black tank to last for a long time before I need to drive to a receiving facility. I don't even want to think about this adult Diaper Genie as an alternative.
Even if boondocking waste can be burned, we are talking about wet waste here, and that will not burn easily or quickly. It would take a large fire and a certain period of time. Dinner would have to be cooked over the campfire either before or after the sewage was combusted, but not during.
For some scenarios, such as people stealthing in urban areas with easy access to trash dumpsters, or people staying in camp grounds with sanitary facilities,... this might be a good partial solution for such folks.