Primo and Rivo are products for different audience
Primo targets people that want to make use of the excellent DAC onboard, with fine-tuned OPAMP output stage with a novel topology, designed from scratch (you won’t find it on any other streamer). You can connect your power amplifier to the analog output of Primo (balanced or unbalanced) and enjoy your music.
Rivo targets people that already have or want to use an external DAC, feeding it with high-quality digital signals. Bits are bits, but the accurate timing when you send them makes the difference between an excellent product, a good product and a bad one. On Rivo all the digital outputs (USB dedicated to a DAC, SPDIF and AES/EBU) have been designed to provide the best digital signal possible to your external DAC.
Primo does have SPDIF and USB ports too. They work fine and they are good, but not as good as the ones on Rivo, because they lack the additional circuits implemented on Rivo to improve the digital signal quality as much as possible. To summarize, the digital outputs on Primo are good, on Rivo are excellent.
The component used on Rivo to provide a better digital signal quality are more expensive than the components used on Primo to provide an excellent analog signal, this is why Rivo costs more than Primo. Another reason is because Rivo required more R&D effort than Primo, which has also an impact on costs
To summarize:
- On Primo, the optimizations are done on the analog path only
- On Rivo, the optimizations are done in three signal paths: USB, SPDIF and AES/EBU
I hope this explains the different prices of the two products 