Maybe you should watch the videos you linked? It's definitely double walled and thicker than even the ooni fyra.
Betello napoli revealed their cost on shark tank to be $83 shipped. That means from walmart it would be less than that which is quite good. And the bertello napoli is dual fuel (gas/wood) AND comes with a perforated peel.
The heat imbalance in those videos is simply because they are cooking with charcoal only (which does not produce a flame) so they have mostly side heat. If they used wood in there mixed with charcoal I think the oven would bake fine and definitely $137 okay.
I did watch the videos. The dome is double walled, not the bottom. And their pizzas are burnt on the top, not the bottom, which means too much top heat, not enough from the stone. Adding a flame, if anything, would burn the top even faster. As I said, it's entirely possible that the videos I watched were still figuring things out, but those video showed a cooler deck and hotter dome than ideal
I have a Bertello, there is no way that it was $83 shipped for the dual fuel option. The gas burner and accessories have a lot of components, some like the safety control and pressure reducing valve are really good quality and not cheap. The wood burning one, I would believe at the time of the TV show: it's just bent sheet metal, rivets and a pizza stone. Today, just shipping has increased many times, let alone everything else. Incidentally, the Bertello is double walled on the bottom
My point was not that the oven is not worth $137. It was that, sometimes, in order to hit a certain price point, the result is not good enough to produce good enough results. Clearly, once you have an enclosed space a a source of heat, you can always bake, for even less than $137. How much control you have on the cooking variables defines how good the result is, though