CostCo are a great place to look for trends in Sonos's range... as soon as they decide to move through a SKU they dump it to CostCo.
Sonance needs to sell more speakers, they sell through Sonos's website to installers who don't question why / how speakers would work with an amp + punters now see it and assume they work together (which they do) or Sonance is somehow the same thing as Sonos. Works for Sonos as they're currently not getting a chunk of the passive speaker market.... so clipping the ticket on Sonance means they get revenue without any warranty / development issues etc.
It would be no different to buying Flexson brackets from Sonos etc.
This industry is not getting cheaper and cheaper, we're simply convincing ourselves that we have to push the cheapest option to customers. #makesonosgreatagain