I think there's a bunch of factors to why yubi have upped their prices - not least, waiting for competition in their form factor & not seeing any emerge (token2 & nitrokey are much bulkier) probably gave them some confidence in the uniqueness of their product offering.

It's also become a much more niche product as software based (and/or primary-device-hardware-based) solutions have evolved & improved. & niche costs more.

All that said I'm really not sure why they've been so quiet on new series releases.